Add .PHONY targets to top Makefile for non-file targets
Add .PHONY targets to top Makefile for non-file targets

When a make target doesn't result in a file of the same name, adding it
to a .PHONY target means make won't look for such a file, speeding the
build up a bit. This allows `make doxygen' to work since otherwise make
will consider the doxygen directory as up to date.

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