mesa: add missing RG_INTEGER and some RED_INTEGER_EXT checks.

mesa: add missing RG_INTEGER and some RED_INTEGER_EXT checks.

This just adds the correct checks and asserts in the right places. This doesn't
fix all the tests that I've sent to piglit, need to add int paths to go alongside the uint paths that don't go via float to fix it up properly.

I'm not sure how much of that could be templated/shared will have a look
once I write it the long way.

Reviewed-by: Brian Paul <brianp@vmware.com>
Signed-off-by: Dave Airlie <airlied@redhat.com>