Factor out common sub-expression from multi-line-comment regular expression.
Factor out common sub-expression from multi-line-comment regular expression.

In two places we look for an (optional) sequence of characters other
than "*" followed by a sequence of on or more "*". Using a name for
this (NON_STARS_THEN_STARS) seems to make it a bit easier to
understand.

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