* hurd/hurd/fd.h: Include <fcntl.h>
(__hurd_at_flags): New function.
* hurd/lookup-at.c (__file_name_lookup_at): Replace flag computation
with call to __hurd_at_flags.
* include/unistd.h (__faccessat, __faccessat_noerrno): Add declaration.
* sysdeps/mach/hurd/access.c (access_common): Move implementation to
__faccessat
(hurd_fail_seterrno, hurd_fail_noerrno): Move to sysdeps/mach/hurd/faccessat.c.
(__access_noerrno): Use __faccessat_common instead of access_common.
(__access): Likewise.
* sysdeps/mach/hurd/euidaccess.c (__euidaccess): Replace implementation
with a call to __faccessat.
* sysdeps/mach/hurd/faccessat.c (faccessat): Rename into...
(__faccessat_common): ... this. Move implementation of __access into it when
AT_FLAGS does not contain AT_EACCESS. Make it call __hurd_at_flags, add
reauthenticate_cwdir_at helper to implement AT mechanism.
(__faccessat_noerrno): New function, just calls __faccessat_common.
(__faccessat): New function, just calls __faccessat_common.
(faccessat): Define weak alias.
* sysdeps/mach/hurd/fchmodat.c: New file.
* sysdeps/mach/hurd/fchownat.c: New file.
* sysdeps/mach/hurd/fxstatat.c: New file.
* sysdeps/mach/hurd/fxstatat64.c: New file.
* sysdeps/mach/hurd/linkat.c: New file.
* sysdeps/mach/hurd/mkdirat.c: New file.
* sysdeps/mach/hurd/openat.c: New file.
* sysdeps/mach/hurd/openat64.c: New file.
* sysdeps/mach/hurd/symlinkat.c: New file.
* sysdeps/mach/hurd/unlinkat.c: New file.
* sysdeps/mach/hurd/xmknod.c (__xmknod): Just call __xmknodat.
Guts move to ...
* sysdeps/mach/hurd/xmknodat.c: ... here, new file.
* hurd/lookup-at.c: New file.
* hurd/Makefile (routines): Add it.
* hurd/hurd/fd.h: Declare __file_name_lookup_at,
__file_name_split_at and __directory_name_split_at.
* hurd/hurd/lookup.h: Declare {,__}hurd_directory_name_split.
* hurd/hurdlookup.c (__hurd_directory_name_split): Use __memrchr
unconditionally.
* sysdeps/mach/hurd/open.c: Define {,__,__libc_,}open64 as aliases.
* sysdeps/mach/hurd/open64.c: New file.