test-shader: guard GLES2 specific changes with COGL_HAS_GLES2
test-shader: guard GLES2 specific changes with COGL_HAS_GLES2

Previously we were using an internal only HAVE_COGL_GLES2 define to
guard GLES 2 specific changes so for instance the precision modifiers
weren't being emitted in the shader source.

http://bugzilla.o-hand.com/show_bug.cgi?id=2178

collects/clutter,jigpu/clutter,heysion/clutter-clone,collects/clutter,djdeath/clutter-android,kerrickstaley/clutter-vala,rkudiyarov/clutter_osx,Distrotech/clutter,Distrotech/clutter,kerrickstaley/clutter-vala,spatulasnout/clutter,spatulasnout/clutter,djdeath/clutter-android,Distrotech/clutter,djdeath/clutter-multithreaded,ebassi/clutter,Distrotech/clutter,collects/clutter,GNOME/clutter,kerrickstaley/clutter-vala,GNOME/clutter,dlespiau/clutter,ebassi/clutter,jigpu/clutter,jigpu/clutter,spatulasnout/clutter,djdeath/clutter-android,collects/clutter,GNOME/clutter,djdeath/clutter-android,heysion/clutter-clone,jigpu/clutter,rkudiyarov/clutter_osx,kerrickstaley/clutter-vala,heysion/clutter-clone,nobled/clutter,djdeath/clutter,djdeath/clutter,djdeath/clutter-android,Distrotech/clutter,jigpu/clutter,nobled/clutter,heysion/clutter-clone,nobled/clutter,GNOME/clutter,Distrotech/clutter,djdeath/clutter-multithreaded,djdeath/clutter,rkudiyarov/clutter_osx,djdeath/clutter-multithreaded,ebassi/clutter,GNOME/clutter,spatulasnout/clutter,dlespiau/clutter,spatulasnout/clutter,dlespiau/clutter,djdeath/clutter,djdeath/clutter,heysion/clutter-clone,rkudiyarov/clutter_osx,djdeath/clutter-multithreaded,ebassi/clutter,collects/clutter,djdeath/clutter,ebassi/clutter,jigpu/clutter