It can't be used with older GLSL. Fixes a crash when attempting to anyway.
Closes: #97 (closed) Fixes: e7308b6c "glamor: Add support for CA rendering in a single pass." Reviewed-by: Dave Airlie airlied@redhat.com Reviewed-by: Kenneth Graunke kenneth@whitecape.org (Cherry picked from commit 5bfca003)