This adds a missing return statement to the non-futex wait-until
operation.

Signed-off-by: Jonathan Wakely <jwakely@redhat.com>

libstdc++-v3/ChangeLog:

	PR libstdc++/102074
	* include/bits/atomic_timed_wait.h (__timed_waiter_pool)
	[!_GLIBCXX_HAVE_PLATFORM_TIMED_WAIT]: Add missing return.

Tested powerpc64le-linux and power-aix and sparc-solaris.

Committed to trunk.

We think there's another issue with return values for the futex case,
which we'll fix separately.