glsl2: Fix lexing of octal values, including "0".
glsl2: Fix lexing of octal values, including "0".

When faced with a constructor like 'ivec4(0, 2, 0, 0)', we would
manage to get a value of 2 instead of 0 for the first "0".  Usually 2
characters past "0" would point at some junk and lex as 0 anyway.

Fixes glsl-octal and glsl-unused-varyings.

dellis1972/glsl-optimizer,zeux/glsl-optimizer,mcanthony/glsl-optimizer,zz85/glsl-optimizer,wolf96/glsl-optimizer,KTXSoftware/glsl2agal,zeux/glsl-optimizer,tokyovigilante/glsl-optimizer,wolf96/glsl-optimizer,zeux/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,benaadams/glsl-optimizer,zeux/glsl-optimizer,djreep81/glsl-optimizer,adobe/glsl2agal,tokyovigilante/glsl-optimizer,zz85/glsl-optimizer,dellis1972/glsl-optimizer,KTXSoftware/glsl2agal,djreep81/glsl-optimizer,mapbox/glsl-optimizer,metora/MesaGLSLCompiler,KTXSoftware/glsl2agal,zz85/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,benaadams/glsl-optimizer,KTXSoftware/glsl2agal,wolf96/glsl-optimizer,adobe/glsl2agal,adobe/glsl2agal,adobe/glsl2agal,bkaradzic/glsl-optimizer,dellis1972/glsl-optimizer,jbarczak/glsl-optimizer,benaadams/glsl-optimizer,djreep81/glsl-optimizer,benaadams/glsl-optimizer,mapbox/glsl-optimizer,jbarczak/glsl-optimizer,zz85/glsl-optimizer,adobe/glsl2agal,zeux/glsl-optimizer,jbarczak/glsl-optimizer,bkaradzic/glsl-optimizer,jbarczak/glsl-optimizer,tokyovigilante/glsl-optimizer,wolf96/glsl-optimizer,djreep81/glsl-optimizer,mapbox/glsl-optimizer,dellis1972/glsl-optimizer,tokyovigilante/glsl-optimizer,tokyovigilante/glsl-optimizer,benaadams/glsl-optimizer,bkaradzic/glsl-optimizer,wolf96/glsl-optimizer,bkaradzic/glsl-optimizer,metora/MesaGLSLCompiler,mapbox/glsl-optimizer,metora/MesaGLSLCompiler,mcanthony/glsl-optimizer,mcanthony/glsl-optimizer,KTXSoftware/glsl2agal,mcanthony/glsl-optimizer,dellis1972/glsl-optimizer,bkaradzic/glsl-optimizer,mcanthony/glsl-optimizer,zz85/glsl-optimizer,mapbox/glsl-optimizer