Fix Xcode 4 build some more

I think I have $ARCHS set up correctly now.
I give up on 64-bit support :-p

Xcode 5 GM (but _not_ the "GM seed") refuses to build 64-bit iOS unless
the deployment target is bumped to 7.0, which we can't do because we
support 6.0. Taking out the 64-bit architecture settings.