Add C wrappers for process_vm_readv/process_vm_writev [BZ #25810]

Since the the U marker can only be applied to 2 unsigned long arguments
in syscalls.list files, add a C wrapper for process_vm_readv and
process_vm_writev syscals which have more than 2 unsigned long arguments.

sysdeps/unix/sysv/linux/process_vm_writev.c

@@ -0,0 +1,32 @@
+/* process_vm_writev - Linux specific syscall.
+   Copyright (C) 2020 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
+   <https://www.gnu.org/licenses/>.  */
+
+#include <unistd.h>
+#include <sysdep.h>
+#include <errno.h>
+#include <sys/uio.h>
+
+ssize_t
+process_vm_writev (pid_t pid, const struct iovec *local_iov,
+		   unsigned long int liovcnt,
+		   const struct iovec *remote_iov,
+		   unsigned long int riovcnt, unsigned long int flags)
+{
+  return INLINE_SYSCALL_CALL (process_vm_writev, pid, local_iov,
+			      liovcnt, remote_iov, riovcnt, flags);
+}