webpmux: warn when odd frame offsets are used
webpmux: warn when odd frame offsets are used

offsets are stored as (x/2, y/2)

Change-Id: Ic8f727ab7996a84c1f8c57f4f6dbaf8701bf8eae

matanbs/webm.libwebp,jiehu5114/libwebp,kleopatra999/webm.libwebp,iniwf/webm.libwebp,imazen/libwebp,ericmckean/webm.libwebp,PKRoma/libwebp,jiehu5114/libwebp,comoyo/gonzo-libwebp,webmproject/libwebp,ya7lelkom/libwebp,PKRoma/libwebp,reimaginemedia/webm.libwebp,Aexyn/libwebp,comoyo/gonzo-libwebp,ttyangf/libwebp,Aexyn/libwebp,appunite/libwebp,Aexyn/libwebp,Aexyn/libwebp,Maria1099/webm.libwebp,webmproject/libwebp,comoyo/gonzo-libwebp,webmproject/libwebp,Acidburn0zzz/webm.libwebp,PKRoma/libwebp,imazen/libwebp,matanbs/webm.libwebp,iniwf/webm.libwebp,kalli123/webm.libwebp,Aexyn/libwebp,jacklicn/libwebp,kleopatra999/webm.libwebp,appunite/libwebp,jacklicn/libwebp,rxl194/libwebp,ya7lelkom/libwebp,matanbs/webm.libwebp,zofuthan/libwebp,gshORTON/webm.libwebp,reimaginemedia/webm.libwebp,Suvarna1488/webm.libwebp,yohunl/libwebp,imazen/libwebp,yohunl/libwebp,imazen/libwebp,altogother/webm.libwebp,Acidburn0zzz/webm.libwebp,Suvarna1488/webm.libwebp,kim42083/webm.libwebp,jiehu5114/libwebp,jiehu5114/libwebp,Suvarna1488/webm.libwebp,Suvarna1488/webm.libwebp,yohunl/libwebp,jacklicn/libwebp,kim42083/webm.libwebp,webmproject/libwebp,ericmckean/webm.libwebp,PKRoma/libwebp,jacklicn/libwebp,Acidburn0zzz/webm.libwebp,gshORTON/webm.libwebp,yohunl/libwebp,comoyo/gonzo-libwebp,kalli123/webm.libwebp,altogother/webm.libwebp,Acidburn0zzz/webm.libwebp,redengineer/libwebp,abwiz0086/webm.libwebp,iniwf/webm.libwebp,iniwf/webm.libwebp,reimaginemedia/webm.libwebp,abwiz0086/webm.libwebp,appunite/libwebp,zofuthan/libwebp,reimaginemedia/webm.libwebp,rxl194/libwebp,kim42083/webm.libwebp,jiehu5114/libwebp,kalli123/webm.libwebp,zofuthan/libwebp,kalli123/webm.libwebp,jacklicn/libwebp,ericmckean/webm.libwebp,appunite/libwebp,ttyangf/libwebp,appunite/libwebp,ya7lelkom/libwebp,imazen/libwebp,gshORTON/webm.libwebp,ya7lelkom/libwebp,ericmckean/webm.libwebp,appunite/libwebp,PKRoma/libwebp,redengineer/libwebp,Maria1099/webm.libwebp,kalli123/webm.libwebp,kleopatra999/webm.libwebp,Maria1099/webm.libwebp,comoyo/gonzo-libwebp,Suvarna1488/webm.libwebp,rxl194/libwebp,gshORTON/webm.libwebp,comoyo/gonzo-libwebp,rxl194/libwebp,ericmckean/webm.libwebp,redengineer/libwebp,abwiz0086/webm.libwebp,altogother/webm.libwebp,ya7lelkom/libwebp,ttyangf/libwebp,rxl194/libwebp,kim42083/webm.libwebp,webmproject/libwebp,Acidburn0zzz/webm.libwebp,altogother/webm.libwebp,kleopatra999/webm.libwebp,kim42083/webm.libwebp,abwiz0086/webm.libwebp,redengineer/libwebp,gshORTON/webm.libwebp,yohunl/libwebp,altogother/webm.libwebp,iniwf/webm.libwebp,matanbs/webm.libwebp,ttyangf/libwebp,matanbs/webm.libwebp,comoyo/gonzo-libwebp,abwiz0086/webm.libwebp,zofuthan/libwebp,ttyangf/libwebp,kleopatra999/webm.libwebp,Maria1099/webm.libwebp,redengineer/libwebp,Maria1099/webm.libwebp,zofuthan/libwebp,reimaginemedia/webm.libwebp,PKRoma/libwebp