Fix for PR libobjc/49883 ("clang + gcc 4.6 runtime = broken") and a small related clang fix

[Mike Stump]

On Oct 9, 2011, at 3:30 AM, Nicola Pero wrote:
> Unfortunately, the report was correct in that clang is producing incorrect code and
> abusing the higher bits of the class->info field to store some other information.

The clang folks are pretty responsive.  I'd always give them a chance to `fix' thier code, before putting hack-arounds in our code in general.

> PS: In case anyone wonders, I do want the GNU Objective-C Runtime to be usable with
> free, non-GCC Objective-C compilers.

I think that's a fine goal.  I like compatibility.