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>

src/mesa/program/prog_statevars.c

@@ -609,6 +609,10 @@ _mesa_fetch_state(struct gl_context *ctx, const gl_state_index state[],
             val[0].i = ctx->TessCtrlProgram.patch_vertices;
          return;
 
+      case STATE_ADVANCED_BLENDING_MODE:
+         val[0].i = ctx->Color.BlendEnabled ? ctx->Color._AdvancedBlendMode : 0;
+         return;
+
       /* XXX: make sure new tokens added here are also handled in the 
        * _mesa_program_state_flags() switch, below.
        */
@@ -719,6 +723,9 @@ _mesa_program_state_flags(const gl_state_index state[STATE_LENGTH])
       case STATE_FB_WPOS_Y_TRANSFORM:
          return _NEW_BUFFERS;
 
+      case STATE_ADVANCED_BLENDING_MODE:
+         return _NEW_COLOR;
+
       default:
          /* unknown state indexes are silently ignored and
          *  no flag set, since it is handled by the driver.
@@ -925,6 +932,9 @@ append_token(char *dst, gl_state_index k)
    case STATE_FB_WPOS_Y_TRANSFORM:
       append(dst, "FbWposYTransform");
       break;
+   case STATE_ADVANCED_BLENDING_MODE:
+      append(dst, "AdvancedBlendingMode");
+      break;
    default:
       /* probably STATE_INTERNAL_DRIVER+i (driver private state) */
       append(dst, "driverState");