Fix warnings in apps/stereo_ground_segmentation.cpp
Fix warnings in apps/stereo_ground_segmentation.cpp

> stereo_ground_segmentation.cpp:269:25: warning: comparison of integers of different signs: 'int' and 'size_type' (aka 'unsigned long') [-Wsign-compare]

... and 5 more.

krips89/pcl_newfeatures,starius/pcl,shivmalhotra/pcl,nikste/pcl,mschoeler/pcl,cascheberg/pcl,stfuchs/pcl,damienjadeduff/pcl,the-glu/pcl,LZRS/pcl,LZRS/pcl,MMiknis/pcl,KevenRing/pcl,closerbibi/pcl,fskuka/pcl,MMiknis/pcl,KevenRing/vlp,krips89/pcl_newfeatures,sbec/pcl,ResByte/pcl,wgapl/pcl,chenxingzhe/pcl,zhangxaochen/pcl,fskuka/pcl,pkuhto/pcl,shyamalschandra/pcl,stfuchs/pcl,wgapl/pcl,ResByte/pcl,lydhr/pcl,mschoeler/pcl,lydhr/pcl,shyamalschandra/pcl,wgapl/pcl,ipa-rmb/pcl,DaikiMaekawa/pcl,sbec/pcl,ResByte/pcl,RufaelDev/pcc-mp3dg,chenxingzhe/pcl,shyamalschandra/pcl,fanxiaochen/mypcltest,pkuhto/pcl,shangwuhencc/pcl,shyamalschandra/pcl,wgapl/pcl,ResByte/pcl,DaikiMaekawa/pcl,the-glu/pcl,simonleonard/pcl,stefanbuettner/pcl,krips89/pcl_newfeatures,3dtof/pcl,lydhr/pcl,kanster/pcl,mikhail-matrosov/pcl,stefanbuettner/pcl,soulsheng/pcl,drmateo/pcl,shivmalhotra/pcl,RufaelDev/pcc-mp3dg,RufaelDev/pcc-mp3dg,nikste/pcl,closerbibi/pcl,Tabjones/pcl,zhangxaochen/pcl,simonleonard/pcl,pkuhto/pcl,cascheberg/pcl,KevenRing/pcl,Tabjones/pcl,locnx1984/pcl,KevenRing/pcl,starius/pcl,chenxingzhe/pcl,3dtof/pcl,stefanbuettner/pcl,cascheberg/pcl,KevenRing/vlp,lydhr/pcl,KevenRing/vlp,LZRS/pcl,shyamalschandra/pcl,locnx1984/pcl,drmateo/pcl,raydtang/pcl,MMiknis/pcl,simonleonard/pcl,cascheberg/pcl,Tabjones/pcl,the-glu/pcl,RufaelDev/pcc-mp3dg,kanster/pcl,lydhr/pcl,krips89/pcl_newfeatures,mikhail-matrosov/pcl,shangwuhencc/pcl,DaikiMaekawa/pcl,sbec/pcl,soulsheng/pcl,damienjadeduff/pcl,starius/pcl,raydtang/pcl,nikste/pcl,KevenRing/pcl,zhangxaochen/pcl,LZRS/pcl,fskuka/pcl,shangwuhencc/pcl,kanster/pcl,the-glu/pcl,DaikiMaekawa/pcl,locnx1984/pcl,KevenRing/vlp,simonleonard/pcl,mschoeler/pcl,MMiknis/pcl,KevenRing/pcl,3dtof/pcl,KevenRing/vlp,sbec/pcl,locnx1984/pcl,DaikiMaekawa/pcl,ipa-rmb/pcl,fanxiaochen/mypcltest,chenxingzhe/pcl,fanxiaochen/mypcltest,damienjadeduff/pcl,stfuchs/pcl,Tabjones/pcl,simonleonard/pcl,mschoeler/pcl,locnx1984/pcl,drmateo/pcl,mikhail-matrosov/pcl,shangwuhencc/pcl,stefanbuettner/pcl,fanxiaochen/mypcltest,mikhail-matrosov/pcl,krips89/pcl_newfeatures,starius/pcl,raydtang/pcl,damienjadeduff/pcl,fanxiaochen/mypcltest,RufaelDev/pcc-mp3dg,3dtof/pcl,nikste/pcl,pkuhto/pcl,lebronzhang/pcl,ipa-rmb/pcl,MMiknis/pcl,closerbibi/pcl,mschoeler/pcl,cascheberg/pcl,raydtang/pcl,chenxingzhe/pcl,wgapl/pcl,shivmalhotra/pcl,3dtof/pcl,stefanbuettner/pcl,ipa-rmb/pcl,lebronzhang/pcl,nikste/pcl,fskuka/pcl,soulsheng/pcl,the-glu/pcl,damienjadeduff/pcl,lebronzhang/pcl,pkuhto/pcl,closerbibi/pcl,shivmalhotra/pcl,shangwuhencc/pcl,drmateo/pcl,mikhail-matrosov/pcl,fskuka/pcl,stfuchs/pcl,zhangxaochen/pcl,soulsheng/pcl,ResByte/pcl,ipa-rmb/pcl,sbec/pcl,kanster/pcl,soulsheng/pcl,starius/pcl,LZRS/pcl,lebronzhang/pcl,drmateo/pcl,shivmalhotra/pcl,stfuchs/pcl,Tabjones/pcl,closerbibi/pcl,zhangxaochen/pcl,raydtang/pcl,lebronzhang/pcl,kanster/pcl