intel: Try to sanely check that formats match for CopyTexImage.

intel: Try to sanely check that formats match for CopyTexImage.

Before, we were going off of a couple of known (hopeful) matches
between internalFormats and the cpp of the read buffer.  Instead, we
can now just look at the gl_format of the two to see if they match.
We should avoid bad blits that might have been possible before, but
also allow different internalFormats to work without having to
enumerate each one.