mesa: Implement a new GL_MESA_tile_raster_order extension.

The intent is to use this extension on vc4 to allow X11 to do overlapping
CopyArea() within a pixmap without first blitting the pixmap to a
temporary.  With associated glamor patches, improves x11perf
-copywinwin100 performance on a Raspberry Pi 3 from ~4700/sec to
~5130/sec, and is an even larger boost to uncomposited window movement
performance (most copywinwin100 copies don't overlap).

v2: Fix glIsEnabled() on the new enums.
v3: Drop the local spec since I'm upstreaming the spec.

Reviewed-by: Nicolai Hähnle <nicolai.haehnle@amd.com>

include/GL/glext.h

@@ -12470,6 +12470,12 @@ GLAPI void APIENTRY glReplacementCodeuiTexCoord2fColor4fNormal3fVertex3fvSUN (co
 #define GL_FOG_SPECULAR_TEXTURE_WIN       0x80EC
 #endif /* GL_WIN_specular_fog */
 
+/* XXX: Get a regenerated header with the enums properly present. */
+#define GL_TILE_RASTER_ORDER_FIXED_MESA          0x8BB8
+#define GL_TILE_RASTER_ORDER_INCREASING_X_MESA   0x8BB9
+#define GL_TILE_RASTER_ORDER_INCREASING_Y_MESA   0x8BBA
+
+
 #ifdef __cplusplus
 }
 #endif