Consolidate Linux open implementation

Consolidate Linux open implementation

This patch consolidates the open Linux syscall implementation on
sysdeps/unix/sysv/linux/open{64}.c.  The changes are:

  1. Remove open{64} from auto-generation syscalls.list.
  2. Add a new open{64}.c implementation.  For architectures that
     define __OFF_T_MATCHES_OFF64_T the default open64 will create
     alias to required open symbols.
  3. Use __NR_openat as default syscall for open{64}.

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/generic/open.c: Remove file.
	* sysdeps/unix/sysv/linux/generic/open64.c: Likewise.
	* sysdeps/unix/sysv/linux/wordsize-64/open64.c: Likewise.
	* sysdeps/unix/sysv/linux/open.c: New file.
	* sysdeps/unix/sysv/linux/open64.c (__libc_open64): Use O_LARGEFILE
	only for __OFF_T_MATCHES_OFF64_T and add alias to open if the case.
	* sysdeps/unix/sysv/linux/wordsize-64/syscalls.list: Remove open
	from auto-generated list.