Remove obsolete, never-implemented XSI STREAMS declarations

The stub implementations are turned into compat symbols.

Linux actually has two reserved system call numbers (for getpmsg
and putpmsg), but these system calls have never been implemented,
and there are no plans to implement them, so this patch replaces
the wrappers with the generic stubs.

According to <https://bugzilla.redhat.com/show_bug.cgi?id=436349

>,
the presence of the XSI STREAMS declarations is a minor portability
hazard because they are not actually implemented.

This commit does not change the TIRPC support code in
sunrpc/rpc_svcout.c.  It uses additional XTI functionality and
therefore never worked with glibc.

Reviewed-by: Carlos O'Donell <carlos@redhat.com>