WIP: Protect concurrent calls to XOpenIM/XCloseIM with a lock

This fixes a bug where concurrent threads call XOpenIM double freeing memory or freezing the process.

Fixes: #31 (closed)

• https://bugs.freedesktop.org/show_bug.cgi?id=69088
• Wine-Bug: https://bugs.winehq.org/show_bug.cgi?id=47366
• https://www.winehq.org/pipermail/wine-devel/2019-September/150677.html

Signed-off-by: Bernhard Übelacker bernhardu@mailbox.org