glsl: Raise linking error if gl_FragDepth layout is inconsistent
glsl: Raise linking error if gl_FragDepth layout is inconsistent

From the AMD_conservative_depth spec:
   If gl_FragDepth is redeclared in any fragment shader in a program, it
   must be redeclared in all fragment shaders in that program that have
   static assignments to gl_FragDepth. All redeclarations of gl_FragDepth in
   all fragment shaders in a single program must have the same set of
   qualifiers.

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