Consolidate pwritev/pwritev64 implementations

Consolidate pwritev/pwritev64 implementations

This patch consolidates all the pwritev{64} implementation for Linux
in only one (sysdeps/unix/sysv/linux/pwritev{64}.c).  It also removes the
syscall from the auto-generation using assembly macros.

It was based on previous pwrite/pwrite64 consolidation patch.  The new macro
SYSCALL_LL{64} is used to handle the offset argument and alias is created
for __ASSUME_OFF_DIFF_OFF64 in case of pread64.

Checked on x86_64, i386, aarch64, and powerpc64le.

	* misc/Makefile (CFLAGS-pwritev.c): New variable: add cancellation
	required flags.
	(CFLAGS-pwritev64.c): Likewise.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/pwritev.c: Remove file.
	* sysdeps/unix/sysv/linux/generic/wordsize-32/pwritev64.c: Likewise.
	* sysdeps/unix/sysv/linux/mips/mips64/n64/pwritev64.c: Likewise.
	* sysdeps/unix/sysv/linux/wordsize-64/pwritev.c: Likewise.
	* sysdeps/unix/sysv/linux/wordsize-64/pwritev64.: Likwise.
	* sysdeps/unix/sysv/linux/x86_64/x32/syscalls.list (pwritev): Remove
	syscall from auto-generation.
	* sysdeps/unix/sysv/linux/pwritev.c: Rewrite implementation.
	[WORDSIZE == 64] (pwritev64): Remove macro.
	[!PWRITEV] (PWRITEV): Likewise.
	[!PWRITEV] (PWRITEV_REPLACEMENT): Likewise.
	[!PWRITEV] (PWRITE): Likewise.
	[!PWRITEV] (OFF_T): Likewise.
	[!__ASSUME_PWRITEV] (PWRITEV_REPLACEMENT): Likewise.
	(LO_HI_LONG): Remove macro.
	[__WORDSIZE != 64 || __ASSUME_OFF_DIFF_OFF64] (pwritev): Add function.
	* sysdeps/unix/sysv/linux/pwritev64.c: Rewrite implementation.
	(PWRITEV): Remove macro.
	(PWRITEV_REPLACEMENTE): Likewise.
	(PWRITE): Likewise.
	(OFF_T): Likewise.
	(pwritev64): New function.
	* nptl/tst-cancel4.c (tf_writev): Add test.