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>

 # Bare metal config options

 config KERNEL_bare_metal

     select BARE_METAL

     help

       'Bare metal' refers to those programs that run without any kernel.

       You probably want to say 'y' here if you plan to use your compiler

       to build bootloaders. It is not yet suitable to build Linux kernels,

       though, because the APCI stuff relies on the target C library headers

       being available?!?!...