Clarified the semantics of the Offset type.
Clarified the semantics of the Offset type.

Change-Id: Iccc36d24321ac4d556692ac715c0cc69a2c9e09e
Tested: on Linux.

alexames/flatbuffers,google/flatbuffers,chenkai036/flatbuffers,stewartmiles/flatbuffers,alexames/flatbuffers,hgl888/flatbuffers,pjulien/flatbuffers,stewartmiles/flatbuffers,stewartmiles/flatbuffers,google/flatbuffers,chenkai036/flatbuffers,jekinchen/flatjni,royalharsh/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,pjulien/flatbuffers,google/flatbuffers,rw/flatbuffers,royalharsh/flatbuffers,endorph-soft/flatbuffers,rw/flatbuffers,google/flatbuffers,DavadDi/flatbuffers,pjulien/flatbuffers,royalharsh/flatbuffers,alexames/flatbuffers,chenkai036/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,google/flatbuffers,rw/flatbuffers,jekinchen/flatjni,evolutional/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,alexames/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,google/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,DavadDi/flatbuffers,rw/flatbuffers,jekinchen/flatjni,pjulien/flatbuffers,royalharsh/flatbuffers,stewartmiles/flatbuffers,alexames/flatbuffers,chenkai036/flatbuffers,jekinchen/flatjni,google/flatbuffers,hgl888/flatbuffers,alexames/flatbuffers,evolutional/flatbuffers,stewartmiles/flatbuffers,rw/flatbuffers,chenkai036/flatbuffers,chenkai036/flatbuffers,rw/flatbuffers,jekinchen/flatjni,jekinchen/flatjni,stewartmiles/flatbuffers,jekinchen/flatjni,pjulien/flatbuffers,DavadDi/flatbuffers,rw/flatbuffers,royalharsh/flatbuffers,stewartmiles/flatbuffers,endorph-soft/flatbuffers,jekinchen/flatjni,evolutional/flatbuffers,google/flatbuffers,royalharsh/flatbuffers,endorph-soft/flatbuffers,endorph-soft/flatbuffers,google/flatbuffers,pjulien/flatbuffers,rw/flatbuffers,jekinchen/flatjni,google/flatbuffers,endorph-soft/flatbuffers,chenkai036/flatbuffers,alexames/flatbuffers,royalharsh/flatbuffers,jekinchen/flatjni,stewartmiles/flatbuffers,alexames/flatbuffers,hgl888/flatbuffers,google/flatbuffers,royalharsh/flatbuffers,google/flatbuffers,endorph-soft/flatbuffers,rw/flatbuffers,endorph-soft/flatbuffers,evolutional/flatbuffers,stewartmiles/flatbuffers,pjulien/flatbuffers,chenkai036/flatbuffers,stewartmiles/flatbuffers,chenkai036/flatbuffers,endorph-soft/flatbuffers,rw/flatbuffers,stewartmiles/flatbuffers,endorph-soft/flatbuffers,hgl888/flatbuffers,pjulien/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,hgl888/flatbuffers,evolutional/flatbuffers,royalharsh/flatbuffers,alexames/flatbuffers,hgl888/flatbuffers,royalharsh/flatbuffers,evolutional/flatbuffers,evolutional/flatbuffers,pjulien/flatbuffers,google/flatbuffers,pjulien/flatbuffers,evolutional/flatbuffers,google/flatbuffers,evolutional/flatbuffers,alexames/flatbuffers,DavadDi/flatbuffers,google/flatbuffers,rw/flatbuffers,stewartmiles/flatbuffers,chenkai036/flatbuffers,rw/flatbuffers,endorph-soft/flatbuffers,alexames/flatbuffers,stewartmiles/flatbuffers