mesa: refactor: move #define FEATURE flags into new mfeatures.h file

Also, check the FEATURE flags in many places.
(cherry picked from commit 40d1a40f29)

Conflicts:

	src/mesa/main/config.h
	src/mesa/main/context.c
	src/mesa/main/texobj.c
	src/mesa/main/texstate.c
	src/mesa/main/texstore.c

src/mesa/main/state.c

@@ -40,7 +40,9 @@
 #include "framebuffer.h"
 #include "light.h"
 #include "matrix.h"
+#if FEATURE_pixel_transfer
 #include "pixel.h"
+#endif
 #include "shader/program.h"
 #include "state.h"
 #include "stencil.h"
@@ -469,8 +471,10 @@ _mesa_update_state_locked( GLcontext *ctx )
    if (new_state & _NEW_STENCIL)
       _mesa_update_stencil( ctx );
 
+#if FEATURE_pixel_transfer
    if (new_state & _IMAGE_NEW_TRANSFER_STATE)
       _mesa_update_pixel( ctx, new_state );
+#endif
 
    if (new_state & _DD_NEW_SEPARATE_SPECULAR)
       update_separate_specular( ctx );