Pull in namespace.h when building all .c files using gcc's -include option,
so that we can provide asm labels for the memcpy/memset/__stack_smash_handler
calls that it generates ab initio. Eliminate direct #includes of it. Make
sure it's a dependency of all objects (unnecessary for asm, but close enough).

ok deraadt@

Hide YP-specific xdr_* functions, and have the YP tools link -lrpcsvc
as needed.
ok miod guenther