mesa: Add ARB_clip_control.xml to automake.

Adding this makes 'make check' catch failures introduced from
within ARB_clip_control.xml earlier.

Signed-off-by: Mathias Froehlich <Mathias.Froehlich@web.de>
diff --git a/src/mapi/glapi/gen/Makefile.am b/src/mapi/glapi/gen/Makefile.am
index 2fbc598..72e5095 100644
--- a/src/mapi/glapi/gen/Makefile.am
+++ b/src/mapi/glapi/gen/Makefile.am
@@ -113,6 +113,7 @@
 	ARB_blend_func_extended.xml \
 	ARB_clear_buffer_object.xml \
 	ARB_clear_texture.xml \
+	ARB_clip_control.xml \
 	ARB_color_buffer_float.xml \
 	ARB_compressed_texture_pixel_storage.xml \
 	ARB_compute_shader.xml \