Consolidate lseek/lseek64/llseek implementations

Consolidate lseek/lseek64/llseek implementations

This patch consolidates all Linux lseek/lseek64/llseek implementation
in on on sysdeps/unix/sysv/linux/lseek{64}.c.  It also removes the llseek
file and instead consolidate the LFS lseek implementation on lseek64.c
as for other LFS symbols implementations.

The general idea is:

  - lseek: ABIs that not define __OFF_T_MATCHES_OFF64_T will preferable
  use __NR__llseek if kernel supports it, otherwise they will use __NR_lseek.
  ABIs that defines __OFF_T_MATCHES_OFF64_T won't produce any symbol.

  - lseek64: ABIs with __OFF_T_MATCHES_OFF64_T will preferable use __NR_lseek
  (since it will use 64-bit arguments without low/high splitting) and
  __NR__llseek if __NR_lseek is not defined (for some ILP32 ports).

  - llseek: files will be removed and symbols will be aliased ot lseek64.

ABI without __OFF_T_MATCHES_OFF64_T and without __NR_llseek (basically MIPS64n32
so far) are covered by building lseek with off_t as expected and lseek64
using __NR_lseek (as expected for off64_t being passed using 64-bit registers).

For this consolidation I mantained the x32 assembly specific implementation
because to correctly fix this it would required both the x32 fix for
{INLINE,INTERNAL}_SYSCALL [1] and a wrapper to correctly subscribe it to
return 64 bits instead of default 32 bits (as for times).  It could a future
cleanup.

It is based on my previous {INTERNAL,INLINE}_SYSCALL_CALL macro [2],
although it is mainly for simplification.

Tested on x86_64, i686, aarch64, armhf, and powerpc64le.

	* nptl/Makefile (libpthread-routines): Remove ptw-llseek and add
	ptw-lseek64.
	* sysdeps/unix/sysv/linux/Makefile (sysdeps_routines): Remove llseek.
	* sysdeps/unix/sysv/linux/alpha/Makefile  (sysdeps_routines):
	Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/llseek.c: Remove file.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/lseek.c: Remove file.
	* sysdeps/unix/sysv/linux/mips/mips64/llseek.c: Likewise.
	* sysdeps/unix/sysv/linux/llseek.c: Remove file.
	* sysdeps/unix/sysv/linux/lseek.c: New file.
	* sysdeps/unix/sysv/linux/lseek64.c: Add default Linux implementation.
	* sysdeps/unix/sysv/linux/mips/mips64/syscalls.list: Remove lseek and
	__libc_lseek64 from auto-generation.
	* sysdeps/unix/sysv/linux/wordsize-64/syscalls.list: Likewise.
	* sysdeps/unix/sysv/linux/x86_64/x32/lseek64.S: New file.

[1] https://sourceware.org/ml/libc-alpha/2016-08/msg00443.html
[2] https://sourceware.org/ml/libc-alpha/2016-08/msg00646.html