posix_types: Make __kernel_[ug]id32_t default to unsigned int

All ports use unsigned int for __kernel_[ug]id32_t, but not all ports
use unsigned int for __kernel_[ug]id_t.  Thus, change the default for
the "32" types so ports don't need to override them.

Signed-off-by: H. Peter Anvin <hpa@zytor.com>
Link: http://lkml.kernel.org/r/1328677745-20121-2-git-send-email-hpa@zytor.com
Cc: Arnd Bergmann <arnd@arndb.de>