Introduce prototype-style definitions for various *at functions.
Upstream, these function definitions were removed in:

commit 754a15c61cd6834685386a134d0a0fed5f3ac4c1
Author: Joseph Myers <joseph@codesourcery.com>
Date:   Tue Sep 30 14:32:08 2014 +0000

    Move some *at definitions to syscalls.list (bug 14138).

diff --git a/sysdeps/unix/sysv/linux/fchownat.c b/sysdeps/unix/sysv/linux/fchownat.c
index 624804fa8cbfd8a1..0673118ad1c72958 100644
--- a/sysdeps/unix/sysv/linux/fchownat.c
+++ b/sysdeps/unix/sysv/linux/fchownat.c
@@ -29,12 +29,7 @@
 
 /* Change the owner and group of FILE.  */
 int
-fchownat (fd, file, owner, group, flag)
-     int fd;
-     const char *file;
-     uid_t owner;
-     gid_t group;
-     int flag;
+fchownat (int fd, const char *file, uid_t owner, gid_t group, int flag)
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/futimesat.c b/sysdeps/unix/sysv/linux/futimesat.c
index e3d034f800dfe61b..77f320d94aef5435 100644
--- a/sysdeps/unix/sysv/linux/futimesat.c
+++ b/sysdeps/unix/sysv/linux/futimesat.c
@@ -29,10 +29,7 @@
 /* Change the access time of FILE relative to FD to TVP[0] and
    the modification time of FILE to TVP[1].  */
 int
-futimesat (fd, file, tvp)
-     int fd;
-     const char *file;
-     const struct timeval tvp[2];
+futimesat (int fd, const char *file, const struct timeval tvp[2])
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/linkat.c b/sysdeps/unix/sysv/linux/linkat.c
index 90e0a79a7014ab72..0526861c007d773f 100644
--- a/sysdeps/unix/sysv/linux/linkat.c
+++ b/sysdeps/unix/sysv/linux/linkat.c
@@ -27,12 +27,7 @@
 /* Make a link to FROM named TO but relative paths in TO and FROM are
    interpreted relative to FROMFD and TOFD respectively.  */
 int
-linkat (fromfd, from, tofd, to, flags)
-     int fromfd;
-     const char *from;
-     int tofd;
-     const char *to;
-     int flags;
+linkat (int fromfd, const char *from, int tofd, const char *to, int flags)
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/mkdirat.c b/sysdeps/unix/sysv/linux/mkdirat.c
index c5ac40ad70c78b62..3989c13f6d511389 100644
--- a/sysdeps/unix/sysv/linux/mkdirat.c
+++ b/sysdeps/unix/sysv/linux/mkdirat.c
@@ -28,10 +28,7 @@
 /* Create a new directory with permission bits MODE.  But interpret
    relative PATH names relative to the directory associated with FD.  */
 int
-mkdirat (fd, file, mode)
-     int fd;
-     const char *file;
-     mode_t mode;
+mkdirat (int fd, const char *file, mode_t mode)
 {
   int res;
 
diff --git a/sysdeps/unix/sysv/linux/readlinkat.c b/sysdeps/unix/sysv/linux/readlinkat.c
index 1638cbb38063477e..05ac0c31743e0d09 100644
--- a/sysdeps/unix/sysv/linux/readlinkat.c
+++ b/sysdeps/unix/sysv/linux/readlinkat.c
@@ -29,11 +29,7 @@
 /* Read the contents of the symbolic link PATH relative to FD into no
    more than LEN bytes of BUF.  */
 ssize_t
-readlinkat (fd, path, buf, len)
-     int fd;
-     const char *path;
-     char *buf;
-     size_t len;
+readlinkat (int fd, const char *path, char *buf, size_t len)
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/renameat.c b/sysdeps/unix/sysv/linux/renameat.c
index 7623f5230306baaf..6b9e87016b17ab6c 100644
--- a/sysdeps/unix/sysv/linux/renameat.c
+++ b/sysdeps/unix/sysv/linux/renameat.c
@@ -104,11 +104,7 @@ __atfct_seterrno_2 (int errval, int fd1, const char *buf1, int fd2,
 
 /* Rename the file OLD relative to OLDFD to NEW relative to NEWFD.  */
 int
-renameat (oldfd, old, newfd, new)
-     int oldfd;
-     const char *old;
-     int newfd;
-     const char *new;
+renameat (int oldfd, const char *old, int newfd, const char *new)
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/symlinkat.c b/sysdeps/unix/sysv/linux/symlinkat.c
index 7e3812914c99ad8c..c8f8be9892dc41db 100644
--- a/sysdeps/unix/sysv/linux/symlinkat.c
+++ b/sysdeps/unix/sysv/linux/symlinkat.c
@@ -28,10 +28,7 @@
 
 /* Make a symbolic link to FROM named TO relative to TOFD.  */
 int
-symlinkat (from, tofd, to)
-     const char *from;
-     int tofd;
-     const char *to;
+symlinkat (const char *from, int tofd, const char *to)
 {
   int result;
 
diff --git a/sysdeps/unix/sysv/linux/unlinkat.c b/sysdeps/unix/sysv/linux/unlinkat.c
index 7c50a2a914486808..d4beb82b065068f7 100644
--- a/sysdeps/unix/sysv/linux/unlinkat.c
+++ b/sysdeps/unix/sysv/linux/unlinkat.c
@@ -29,10 +29,7 @@
 
 /* Remove the link named NAME.  */
 int
-unlinkat (fd, file, flag)
-     int fd;
-     const char *file;
-     int flag;
+unlinkat (int fd, const char *file, int flag)
 {
   int result;