Add a new API glamor_create_gc.

As at ValidateGC stage, it may need to touch the pixmap directly, for
example the tile pixmap. We must export this interface to DDX driver
and let the DDX driver to route the processing to us. As this pixmap
may be a texture only pixmap, and DDX don't know how to handle it.

Signed-off-by: Zhigang Gong <zhigang.gong@linux.intel.com>

glamor/glamor.h

@@ -182,6 +182,7 @@ extern _X_EXPORT void glamor_egl_free_screen(int scrnIndex, int flags);
 
 #endif
 
+extern _X_EXPORT int glamor_create_gc(GCPtr gc);
 /* Glamor rendering/drawing functions with XXX_nf. 
  * nf means no fallback within glamor internal if possible. If glamor
  * fail to accelerate the operation, glamor will return a false, and the