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>

src/mapi/glapi/gen/MESA_tile_raster_order.xml

@@ -0,0 +1,13 @@
+<?xml version="1.0"?>
+<!DOCTYPE OpenGLAPI SYSTEM "gl_API.dtd">
+
+<OpenGLAPI>
+
+<!-- XXX: need an extension number -->
+<category name="GL_MESA_tile_rasterizer_order">
+    <enum name="TILE_RASTER_ORDER_FIXED_MESA"              value="0x8BB8"/>
+    <enum name="TILE_RASTER_ORDER_INCREASING_X_MESA"       value="0x8BB9"/>
+    <enum name="TILE_RASTER_ORDER_INCREASING_Y_MESA"       value="0x8BBA"/>
+</category>
+
+</OpenGLAPI>

src/mapi/glapi/gen/Makefile.am

@@ -210,6 +210,7 @@ API_XML = \
 	KHR_robustness.xml \
 	KHR_robustness_es.xml \
 	KHR_texture_compression_astc.xml \
+	MESA_tile_raster_order.xml \
 	NV_conditional_render.xml \
 	NV_primitive_restart.xml \
 	NV_texture_barrier.xml \