libc/glibc: workaround for autoconf'ed define of caddr_t

When building canadian cross compiler, I have some trouble with
configure defining caddr_t as a macro, like:
#define caddr_t char *

When combined with the types.h where caddr_t is protected together
with daddr_t, the typedef of caddr_t breaks.

This patch works around it by protecting the caddr_t typedef
specifically.

I am uncertain as to the real cause and solution to this :-(

Signed-off-by: Esben Haabendal <eha@dev.doredevelopment.dk>

# Super-H specific configuration file

config ARCH_sh

    select ARCH_SUPPORTS_32

    select ARCH_DEFAULT_32

    select ARCH_USE_MMU

    select ARCH_SUPPORTS_BOTH_ENDIAN

    select ARCH_DEFAULT_LE

    help

      The Super-H architecture, as defined by:

        http://www.renesas.com/fmwk.jsp?cnt=superh_family_landing.jsp&fp=/products/mpumcu/superh_family/