i965: Claim to support 4 multisamples on gen6+.

We're not quite ready to actually support it in the implementation,
but at least this allows GL 3.0 API-reliant applications to hopefully
run successfully, though they won't get multisampling.

Reviewed-by: Kenneth Graunke <kenneth@whitecape.org>

src/mesa/drivers/dri/i965/brw_context.c

@@ -208,6 +208,14 @@ brwCreateContext(int api,
    ctx->Const.MaxTransformFeedbackSeparateComponents =
       BRW_MAX_SOL_BINDINGS / BRW_MAX_SOL_BUFFERS;
 
+   /* Claim to support 4 multisamples, even though we don't.  This is a
+    * requirement for GL 3.0 that we missed until the last minute.  Go ahead and
+    * claim the limit, so that usage of the 4 multisample-based API that is
+    * guaranteed in 3.0 succeeds, even though we only rasterize a single sample.
+    */
+   if (intel->gen >= 6)
+      ctx->Const.MaxSamples = 4;
+
    /* if conformance mode is set, swrast can handle any size AA point */
    ctx->Const.MaxPointSizeAA = 255.0;