[PATCH 0/1] MR6985: win32u: Release the Win16 mutex when yielding in peek_message.

[Rémi Bernon (＠rbernon)]

This is important for other Win16 threads to have a chance to execute
during peek_message, even if no messages are received, or if the thread
is within a nested window message procedure call.

Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=57384