draw: allow overflows in the llvm paths

draw: allow overflows in the llvm paths

Because our code couldn't handle it we were skipping rendering
if we detected overflows. According to the spec we should
still render but with all 0 vertices, which is what the llvm
code already does. So for the llvm paths lets enable processing
even if an overflow condition has been detected.

Signed-off-by: Zack Rusin <zackr@vmware.com>
Reviewed-by: Jose Fonseca <jfonseca@vmware.com>
Reviewed-by: Roland Scheidegger <sroland@vmware.com>