Make llseek a compat symbol (bug 18471).

Make llseek a compat symbol (bug 18471).

The llseek function name is an obsolete, Linux-specific, unprototyped
name for lseek64 with a link-time warning.  This patch completes the
obsoletion of this function name by making it into a compat symbol,
not available for newly linked programs and not included in the ABI
for new ports.

When a compat symbol is defined in syscalls.list, the code for that
function is not built at all for static linking unless some non-compat
symbol for that function is also defined with an explicit symbol
version, so an explicit symbol version for lseek64 is added to the
MIPS n32 syscalls.list.  The case in make-syscalls.sh that handles
such explicit non-compat symbol versions then needs to be changed to
use weak_alias instead of strong_alias when the syscall is built
outside of libc, to avoid linknamespace failures from a strong lseek64
symbol in static libpthread.

The x32 llseek.S was as far as I could tell already unused (nothing
builds an llseek.* source file, at least since the lseek / lseek64 /
llseek consolidation), so is removed in this patch as well.

Tested for x86_64 and x86, and with build-many-glibcs.py.

	[BZ #18471]
	* sysdeps/unix/make-syscalls.sh (emit_weak_aliases): Use weak
	aliases for non-libc case of versioned symbols.
	* sysdeps/unix/sysv/linux/lseek64.c: Include <shlib-compat.h>.
	(llseek): Define as compat symbol if
	[SHLIB_COMPAT (libc, GLIBC_2_0, GLIBC_2_28)], not as weak alias
	with link warning.
	* sysdeps/unix/sysv/linux/mips/mips64/n32/syscalls.list (llseek):
	Make into a compat symbol, disabled for minimum symbol version
	GLIBC_2.28 and later.
	* sysdeps/unix/sysv/linux/x86_64/x32/llseek.S: Remove file.