Simplify calling conventions of functions under expand_token_list_onto.
Simplify calling conventions of functions under expand_token_list_onto.

We previously had a confusing thing where _expand_token_onto would
return a non-zero value to indicate that the caller should then call
_expand_function_onto. It's much cleaner for _expand_token_onto to
just do what's needed and call the necessary function.

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