Fixed required field checking incorrectly using unsigned offsets.
Fixed required field checking incorrectly using unsigned offsets.

Reported by: https://github.com/google/flatbuffers/issues/99

Change-Id: Ia26da95bbac189836c257fa85f3bec1b153b6207
Tested: on Linux.

hgl888/flatbuffers,wingahi/flatbuffers,DavadDi/flatbuffers,radent/flatbuffers,DreamHill/flatbuffers,JackLian/flatbuffers,hryang/flatbuffers,fuchsia-mirror/third_party-flatbuffers,aeneid/flatbuffers,MiCHiLU/flatbuffers,Reimerei/flatbuffers,eburkitt/flatbuffers,evolutional/flatbuffers,alarouche/flatbuffers,endorph-soft/flatbuffers,mormegil-cz/flatbuffers,kadirahq/flatbuffers,tieusangaka/flatbuffers,yiliaofan/flatbuffers,hanhailong/flatbuffers,SinbadFreedom/FlatBuffer,evolutional/flatbuffers,kadirahq/flatbuffers,vitalyisaev2/flatbuffers,ajrulez/flatbuffers,benssson/flatbuffers,layzerar/flatbuffers,bog-dan-ro/flatbuffers,iperry/flatbuffers,vitalyisaev2/flatbuffers,FrankStain/flatbuffers,RAldrich/flatbuffers,xiaPier/flatbuffers,iperry/flatbuffers,lulufei/flatbuffers,stewartmiles/flatbuffers,Belxjander/flatbuffers,marschall/flatbuffers,splhack/flatbuffers,Belxjander/flatbuffers,xiaPier/flatbuffers,MiCHiLU/flatbuffers,dwillmer/flatbuffers,RyanTech/flatbuffers,arbitrary-cat/flatbuffers,fuchsia-mirror/third_party-flatbuffers,wheelcomplex/flatbuffers,KeronTeam/flatbuffers,cogumbreiro/flatbuffers,vanloswang/flatbuffers,cogumbreiro/flatbuffers,splhack/flatbuffers,benssson/flatbuffers,jasonstubbs/flatbuffers,BlueBrain/flatbuffers,FrankStain/flatbuffers,dwillmer/flatbuffers,DavadDi/flatbuffers,ajrulez/flatbuffers,Reimerei/flatbuffers,vitalyisaev2/flatbuffers,MiCHiLU/flatbuffers,Volcanoscar/flatbuffers,Belxjander/flatbuffers,uus169/flatbuffers,endorph-soft/flatbuffers,kusharami/flatbuffers,FrankStain/flatbuffers,pjulien/flatbuffers,wingahi/flatbuffers,EricLagergren/flatbuffers,royalharsh/flatbuffers,DreamHill/flatbuffers,fengshao0907/flatbuffers,alarouche/flatbuffers,davidnasar/flatbuffers,evolutional/flatbuffers,evanw/flatbuffers,xudeheng/flatbuffers,jackyglony/flatbuffers,1yvT0s/flatbuffers,SinbadFreedom/FlatBuffer,hgl888/flatbuffers,1yvT0s/flatbuffers,yiliaofan/flatbuffers,bog-dan-ro/flatbuffers,JackLian/flatbuffers,wheelcomplex/flatbuffers,i17c/flatbuffers,rdumusc/flatbuffers,layzerar/flatbuffers,EricLagergren/flatbuffers,chobie/flatbuffers,alexames/flatbuffers,i17c/flatbuffers,google/flatbuffers,felixguendling/flatbuffers,benssson/flatbuffers,zhuxiaohao/flatbuffers,kusharami/flatbuffers,alexames/flatbuffers,vitalyisaev2/flatbuffers,chobie/flatbuffers,uus169/flatbuffers,xiaPier/flatbuffers,jasonstubbs/flatbuffers,alexames/flatbuffers,xudeheng/flatbuffers,evanw/flatbuffers,vanloswang/flatbuffers,Volcanoscar/flatbuffers,yiliaofan/flatbuffers,alexames/flatbuffers,arbitrary-cat/flatbuffers,cogumbreiro/flatbuffers,eburkitt/flatbuffers,vitalyisaev2/flatbuffers,chobie/flatbuffers,felixguendling/flatbuffers,jekinchen/flatjni,marschall/flatbuffers,stewartmiles/flatbuffers,RyanTech/flatbuffers,felixguendling/flatbuffers,RAldrich/flatbuffers,jasonstubbs/flatbuffers,royalharsh/flatbuffers,vanloswang/flatbuffers,rdumusc/flatbuffers,ajrulez/flatbuffers,fengshao0907/flatbuffers,jbrads/flatbuffers,alexames/flatbuffers,layzerar/flatbuffers,EricLagergren/flatbuffers,zhuxiaohao/flatbuffers,kadirahq/flatbuffers,DreamHill/flatbuffers,davidnasar/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,ajrulez/flatbuffers,1yvT0s/flatbuffers,stewartmiles/flatbuffers,layzerar/flatbuffers,layzerar/flatbuffers,arbitrary-cat/flatbuffers,zhuxiaohao/flatbuffers,xudeheng/flatbuffers,EricLagergren/flatbuffers,tieusangaka/flatbuffers,stewartmiles/flatbuffers,pjulien/flatbuffers,onecityuni/flatbuffers,ThomasBrixLarsen/flatbuffers,stewartmiles/flatbuffers,kiyoto-suzuki/flatbuffers,lulufei/flatbuffers,eproxus/flatbuffers,google/flatbuffers,jackyglony/flatbuffers,robertfsegal/flatbuffers,radent/flatbuffers,lulufei/flatbuffers,chenkai036/flatbuffers,rdumusc/flatbuffers,alexames/flatbuffers,layzerar/flatbuffers,MiCHiLU/flatbuffers,stewartmiles/flatbuffers,RAldrich/flatbuffers,mormegil-cz/flatbuffers,hanhailong/flatbuffers,i17c/flatbuffers,yaolinz/flatbuffers,wheelcomplex/flatbuffers,RyanTech/flatbuffers,guker/flatbuffers,KeronTeam/flatbuffers,onecityuni/flatbuffers,ThomasBrixLarsen/flatbuffers,pjulien/flatbuffers,guker/flatbuffers,eburkitt/flatbuffers,RyanTech/flatbuffers,stewartmiles/flatbuffers,alarouche/flatbuffers,jasonstubbs/flatbuffers,eproxus/flatbuffers,madvay/flatbuffers,jasonstubbs/flatbuffers,SinbadFreedom/FlatBuffer,pjulien/flatbuffers,marschall/flatbuffers,Reimerei/flatbuffers,evanw/flatbuffers,iperry/flatbuffers,RyanTech/flatbuffers,google/flatbuffers,fuchsia-mirror/third_party-flatbuffers,robertfsegal/flatbuffers,evanw/flatbuffers,wuyan6293/flatbuffers,wheelcomplex/flatbuffers,zarianw/flatbuffers,EricLagergren/flatbuffers,robertfsegal/flatbuffers,yiliaofan/flatbuffers,ThomasBrixLarsen/flatbuffers,FrankStain/flatbuffers,DavadDi/flatbuffers,wingahi/flatbuffers,yiliaofan/flatbuffers,FrankStain/flatbuffers,zarianw/flatbuffers,kadirahq/flatbuffers,wuyan6293/flatbuffers,yaolinz/flatbuffers,jekinchen/flatjni,madvay/flatbuffers,MiCHiLU/flatbuffers,hanhailong/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,jekinchen/flatjni,yaolinz/flatbuffers,RAldrich/flatbuffers,zhuxiaohao/flatbuffers,davidnasar/flatbuffers,aeneid/flatbuffers,endorph-soft/flatbuffers,Volcanoscar/flatbuffers,rw/flatbuffers,guker/flatbuffers,stewartmiles/flatbuffers,aeneid/flatbuffers,brunoqc/flatbuffers,SinbadFreedom/FlatBuffer,radent/flatbuffers,Reimerei/flatbuffers,kiyoto-suzuki/flatbuffers,felixguendling/flatbuffers,cogumbreiro/flatbuffers,lulufei/flatbuffers,ajrulez/flatbuffers,fengshao0907/flatbuffers,zarianw/flatbuffers,fuchsia-mirror/third_party-flatbuffers,jbrads/flatbuffers,pjulien/flatbuffers,royalharsh/flatbuffers,royalharsh/flatbuffers,alexames/flatbuffers,ThomasBrixLarsen/flatbuffers,yiliaofan/flatbuffers,aeneid/flatbuffers,dwillmer/flatbuffers,evolutional/flatbuffers,kiyoto-suzuki/flatbuffers,1yvT0s/flatbuffers,jbrads/flatbuffers,MiCHiLU/flatbuffers,xudeheng/flatbuffers,rdumusc/flatbuffers,marschall/flatbuffers,kusharami/flatbuffers,kadirahq/flatbuffers,kiyoto-suzuki/flatbuffers,JackLian/flatbuffers,pakoito/flatbuffers,xudeheng/flatbuffers,zarianw/flatbuffers,rdumusc/flatbuffers,EricLagergren/flatbuffers,jekinchen/flatjni,davidnasar/flatbuffers,hgl888/flatbuffers,pjulien/flatbuffers,bog-dan-ro/flatbuffers,cogumbreiro/flatbuffers,uus169/flatbuffers,xiaPier/flatbuffers,endorph-soft/flatbuffers,aeneid/flatbuffers,hgl888/flatbuffers,evolutional/flatbuffers,madvay/flatbuffers,royalharsh/flatbuffers,hryang/flatbuffers,google/flatbuffers,yaolinz/flatbuffers,pjulien/flatbuffers,1yvT0s/flatbuffers,JackLian/flatbuffers,stewartmiles/flatbuffers,zhuxiaohao/flatbuffers,pakoito/flatbuffers,i17c/flatbuffers,Belxjander/flatbuffers,kiyoto-suzuki/flatbuffers,jekinchen/flatjni,Volcanoscar/flatbuffers,google/flatbuffers,wuyan6293/flatbuffers,zarianw/flatbuffers,rw/flatbuffers,kiyoto-suzuki/flatbuffers,xiaPier/flatbuffers,chenkai036/flatbuffers,evanw/flatbuffers,iperry/flatbuffers,rw/flatbuffers,jbrads/flatbuffers,cogumbreiro/flatbuffers,jbrads/flatbuffers,evolutional/flatbuffers,endorph-soft/flatbuffers,hryang/flatbuffers,kadirahq/flatbuffers,DavadDi/flatbuffers,kiyoto-suzuki/flatbuffers,benssson/flatbuffers,zarianw/flatbuffers,google/flatbuffers,kadirahq/flatbuffers,alexames/flatbuffers,google/flatbuffers,SinbadFreedom/FlatBuffer,google/flatbuffers,jbrads/flatbuffers,pjulien/flatbuffers,endorph-soft/flatbuffers,lulufei/flatbuffers,radent/flatbuffers,chenkai036/flatbuffers,alarouche/flatbuffers,xiaPier/flatbuffers,EricLagergren/flatbuffers,Volcanoscar/flatbuffers,evolutional/flatbuffers,jekinchen/flatjni,radent/flatbuffers,DavadDi/flatbuffers,bog-dan-ro/flatbuffers,chobie/flatbuffers,MiCHiLU/flatbuffers,BlueBrain/flatbuffers,tieusangaka/flatbuffers,pakoito/flatbuffers,wuyan6293/flatbuffers,royalharsh/flatbuffers,brunoqc/flatbuffers,benssson/flatbuffers,arbitrary-cat/flatbuffers,vitalyisaev2/flatbuffers,jekinchen/flatjni,rw/flatbuffers,jasonstubbs/flatbuffers,eburkitt/flatbuffers,jackyglony/flatbuffers,KeronTeam/flatbuffers,eburkitt/flatbuffers,guker/flatbuffers,vanloswang/flatbuffers,kusharami/flatbuffers,endorph-soft/flatbuffers,Reimerei/flatbuffers,mormegil-cz/flatbuffers,jasonstubbs/flatbuffers,jekinchen/flatjni,mormegil-cz/flatbuffers,uus169/flatbuffers,RAldrich/flatbuffers,tieusangaka/flatbuffers,benssson/flatbuffers,wingahi/flatbuffers,fuchsia-mirror/third_party-flatbuffers,chenkai036/flatbuffers,onecityuni/flatbuffers,rw/flatbuffers,hanhailong/flatbuffers,wheelcomplex/flatbuffers,wuyan6293/flatbuffers,fengshao0907/flatbuffers,DreamHill/flatbuffers,dwillmer/flatbuffers,rw/flatbuffers,wheelcomplex/flatbuffers,bog-dan-ro/flatbuffers,bog-dan-ro/flatbuffers,benssson/flatbuffers,layzerar/flatbuffers,eburkitt/flatbuffers,eburkitt/flatbuffers,mormegil-cz/flatbuffers,alexames/flatbuffers,BlueBrain/flatbuffers,splhack/flatbuffers,Belxjander/flatbuffers,SinbadFreedom/FlatBuffer,evolutional/flatbuffers,wingahi/flatbuffers,alarouche/flatbuffers,Reimerei/flatbuffers,rw/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,splhack/flatbuffers,stewartmiles/flatbuffers,hanhailong/flatbuffers,KeronTeam/flatbuffers,chenkai036/flatbuffers,chobie/flatbuffers,DreamHill/flatbuffers,splhack/flatbuffers,DavadDi/flatbuffers,brunoqc/flatbuffers,evolutional/flatbuffers,eproxus/flatbuffers,kusharami/flatbuffers,iperry/flatbuffers,wingahi/flatbuffers,davidnasar/flatbuffers,wheelcomplex/flatbuffers,pjulien/flatbuffers,rw/flatbuffers,splhack/flatbuffers,hanhailong/flatbuffers,fuchsia-mirror/third_party-flatbuffers,bog-dan-ro/flatbuffers,kiyoto-suzuki/flatbuffers,wuyan6293/flatbuffers,chenkai036/flatbuffers,brunoqc/flatbuffers,eproxus/flatbuffers,RyanTech/flatbuffers,eproxus/flatbuffers,vanloswang/flatbuffers,google/flatbuffers,dwillmer/flatbuffers,guker/flatbuffers,kiyoto-suzuki/flatbuffers,robertfsegal/flatbuffers,stewartmiles/flatbuffers,eproxus/flatbuffers,ajrulez/flatbuffers,google/flatbuffers,jekinchen/flatjni,KeronTeam/flatbuffers,rw/flatbuffers,tieusangaka/flatbuffers,marschall/flatbuffers,felixguendling/flatbuffers,rdumusc/flatbuffers,fengshao0907/flatbuffers,mormegil-cz/flatbuffers,madvay/flatbuffers,brunoqc/flatbuffers,wheelcomplex/flatbuffers,onecityuni/flatbuffers,SinbadFreedom/FlatBuffer,endorph-soft/flatbuffers,chenkai036/flatbuffers,jbrads/flatbuffers,evolutional/flatbuffers,alarouche/flatbuffers,royalharsh/flatbuffers,fengshao0907/flatbuffers,evanw/flatbuffers,pakoito/flatbuffers,rw/flatbuffers,fuchsia-mirror/third_party-flatbuffers,lulufei/flatbuffers,chobie/flatbuffers,hgl888/flatbuffers,onecityuni/flatbuffers,vanloswang/flatbuffers,evolutional/flatbuffers,jasonstubbs/flatbuffers,hryang/flatbuffers,jackyglony/flatbuffers,robertfsegal/flatbuffers,pjulien/flatbuffers,google/flatbuffers,chenkai036/flatbuffers,brunoqc/flatbuffers,JackLian/flatbuffers,ThomasBrixLarsen/flatbuffers,royalharsh/flatbuffers,Belxjander/flatbuffers,google/flatbuffers,splhack/flatbuffers,felixguendling/flatbuffers,marschall/flatbuffers,madvay/flatbuffers,hgl888/flatbuffers,SinbadFreedom/FlatBuffer,stewartmiles/flatbuffers,robertfsegal/flatbuffers,davidnasar/flatbuffers,hryang/flatbuffers,fuchsia-mirror/third_party-flatbuffers,evanw/flatbuffers,dwillmer/flatbuffers,FrankStain/flatbuffers,alexames/flatbuffers,BlueBrain/flatbuffers,kadirahq/flatbuffers,alexames/flatbuffers,arbitrary-cat/flatbuffers,rw/flatbuffers,endorph-soft/flatbuffers,royalharsh/flatbuffers,zhuxiaohao/flatbuffers,splhack/flatbuffers,eburkitt/flatbuffers,i17c/flatbuffers,BlueBrain/flatbuffers,i17c/flatbuffers,rw/flatbuffers,jackyglony/flatbuffers,endorph-soft/flatbuffers,zarianw/flatbuffers,pakoito/flatbuffers,FrankStain/flatbuffers,chenkai036/flatbuffers,chobie/flatbuffers,zarianw/flatbuffers,benssson/flatbuffers,BlueBrain/flatbuffers,vitalyisaev2/flatbuffers,google/flatbuffers,bog-dan-ro/flatbuffers,Reimerei/flatbuffers,vitalyisaev2/flatbuffers,ThomasBrixLarsen/flatbuffers,pakoito/flatbuffers,pjulien/flatbuffers,tieusangaka/flatbuffers,Volcanoscar/flatbuffers,1yvT0s/flatbuffers,chobie/flatbuffers,aeneid/flatbuffers,iperry/flatbuffers,uus169/flatbuffers,iperry/flatbuffers,uus169/flatbuffers,chenkai036/flatbuffers,JackLian/flatbuffers,alexames/flatbuffers,evanw/flatbuffers,RAldrich/flatbuffers,yaolinz/flatbuffers,stewartmiles/flatbuffers,EricLagergren/flatbuffers,MiCHiLU/flatbuffers,KeronTeam/flatbuffers,yaolinz/flatbuffers,FrankStain/flatbuffers,guker/flatbuffers,royalharsh/flatbuffers,hryang/flatbuffers,jekinchen/flatjni,iperry/flatbuffers,google/flatbuffers,jackyglony/flatbuffers,jbrads/flatbuffers,DreamHill/flatbuffers,google/flatbuffers,xudeheng/flatbuffers