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>

sysdeps/s390/bits/xtitypes.h

@@ -1,33 +0,0 @@
-/* bits/xtitypes.h -- Define some types used by <bits/stropts.h>.  S390/S390x
-   Copyright (C) 2002-2019 Free Software Foundation, Inc.
-   This file is part of the GNU C Library.
-
-   The GNU C Library is free software; you can redistribute it and/or
-   modify it under the terms of the GNU Lesser General Public
-   License as published by the Free Software Foundation; either
-   version 2.1 of the License, or (at your option) any later version.
-
-   The GNU C Library is distributed in the hope that it will be useful,
-   but WITHOUT ANY WARRANTY; without even the implied warranty of
-   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
-   Lesser General Public License for more details.
-
-   You should have received a copy of the GNU Lesser General Public
-   License along with the GNU C Library; if not, see
-   <http://www.gnu.org/licenses/>.  */
-
-#ifndef _STROPTS_H
-# error "Never include <bits/xtitypes.h> directly; use <stropts.h> instead."
-#endif
-
-#ifndef _BITS_XTITYPES_H
-#define _BITS_XTITYPES_H	1
-
-#include <bits/types.h>
-
-/* This type is used by some structs in <bits/stropts.h>.  */
-typedef __S32_TYPE __t_scalar_t;
-typedef __U32_TYPE __t_uscalar_t;
-
-
-#endif /* bits/xtitypes.h */