Don't use INTUSE with __adjtimex (bug 14132).

Don't use INTUSE with __adjtimex (bug 14132).

Bug 14132 is removal of the old INTDEF/INTUSE system of *_internal
aliases as obsoleted by the hidden_proto / hidden_def system.  Various
cases were cleaned up in 2012, but some remain.  This patch removes
the use of this mechanism for __adjtimex.

Tested for x86_64 that stripped installed shared libraries are
unchanged by the patch.

	[BZ #14132]
	* sysdeps/unix/sysv/linux/include/sys/timex.h: New file.
	* sysdeps/unix/sysv/linux/adjtime.c [!ADJTIMEX] (ADJTIMEX): Do not
	use INTUSE.
	[!ADJTIMEX] (INTUSE(__adjtimex)): Remove declaration.
	* sysdeps/unix/sysv/linux/alpha/adjtime.c (__adjtimex_internal):
	Remove alias.
	(__adjtimex): Define using libc_hidden_ver.
	* sysdeps/unix/sysv/linux/ntp_gettime.c (INTUSE(__adjtimex)):
	Remove declaration.
	(ntp_gettime): Call __adjtimex directly.
	* sysdeps/unix/sysv/linux/ntp_gettimex.c (INTUSE(__adjtimex)):
	Remove declaration.
	(ntp_gettimex): Call __adjtimex directly.
	* sysdeps/unix/sysv/linux/syscalls.list (adjtimex): Remove
	__adjtimex_internal alias.