Rémi found a regression caused by that patch. His analysis suggests
that it's probably correct for NtYieldExecution() to map to
sched_yield().

Let's revert the patch and fix the issue in a slightly different way.

This reverts commit b1a79c6b.
Signed-off-by: Matteo Bruni <mbruni@codeweavers.com>
Signed-off-by: Alexandre Julliard <julliard@winehq.org>