* posix/unistd.h [__USE_ATFILE]: Declare faccessat. * io/faccessat.c: New file. * sysdeps/unix/sysv/linux/faccessat.c: New file. * io/Makefile (routines): Add faccessat. * io/Versions (libc: GLIBC_2.4): Likewise. * io/tst-faccessat.c: New file. * io/Makefile (tests): Add it. * io/sys/stat.h: Likewise.