compiler: Add a new STATE_VAR_ADVANCED_BLENDING_MODE built-in uniform.

This will be used for emulating GL_KHR_advanced_blend_equation features
in shader code.  We'll pass in the blending mode that's in use, and use
that in (effectively) a switch statement in the shader.

v2: Use the new _AdvancedBlendMode field.

Signed-off-by: Kenneth Graunke <kenneth@whitecape.org>
Reviewed-by: Francisco Jerez <currojerez@riseup.net>
diff --git a/src/mesa/program/prog_statevars.h b/src/mesa/program/prog_statevars.h
index e716d90..7fecb37 100644
--- a/src/mesa/program/prog_statevars.h
+++ b/src/mesa/program/prog_statevars.h
@@ -130,6 +130,11 @@
    STATE_FB_WPOS_Y_TRANSFORM,   /**< (1, 0, -1, height) if a FBO is bound, (-1, height, 1, 0) otherwise */
    STATE_TCS_PATCH_VERTICES_IN, /**< gl_PatchVerticesIn for TCS (integer) */
    STATE_TES_PATCH_VERTICES_IN, /**< gl_PatchVerticesIn for TES (integer) */
+   /**
+    * A single enum gl_blend_support_qualifier value representing the
+    * currently active advanced blending equation, or zero if disabled.
+    */
+   STATE_ADVANCED_BLENDING_MODE,
    STATE_INTERNAL_DRIVER	/* first available state index for drivers (must be last) */
 } gl_state_index;