This patch consolidates the open Linux syscall implementation on
sysdeps/unix/sysv/linux/open{64}.c. The changes are:
1. Remove wordsize-64 openat{64}.
2. For architetures that define __OFF_T_MATCHES_OFF64_T openat64
will be default one with alias to required symbols. Otherwise
openat64 will pass the required O_LARGEFILE flag on syscall.
Checked on i686-linux-gnu, x86_64-linux-gnu, x86_64-linux-gnux32,
arch64-linux-gnu, arm-linux-gnueabihf, and powerpc64le-linux-gnu.
* sysdeps/unix/sysv/linux/openat.c (__libc_openat): Build only
for !__OFF_T_MATCHES_OFF64_T.
* sysdeps/unix/sysv/linux/openat64.c (__libc_openat64): New
implementation based on open64.
* sysdeps/unix/sysv/linux/wordsize-64/openat.c: Remove file.
* sysdeps/unix/sysv/linux/wordsize-64/openat64.c: Likewise.
* io/Makefile (routines): Add openat and openat64.
(tests): Add tst-openat.
* io/Versions: Add openat and openat64 for GLIBC_2.4.
* sysdeps/generic/openat.c: New file.
* sysdeps/generic/openat64.c: New file.
* sysdeps/unix/sysv/linux/openat.c: New file.
* sysdeps/unix/sysv/linux/openat64.c: New file.
* io/tst-openat.c: New file.
* sysdeps/unix/sysv/linux/device-nrs.h: Add info for /dev/full.