https://bugs.winehq.org/show_bug.cgi?id=48965
--- Comment #22 from Marko Friedemann mfr@bmx-chemnitz.de --- Alright, I found the ALT key to be configured for "Key to show the menu bar while pressed" in the Ubuntu Unity Plugin for compiz.
Reconfigured it to use the MENU key instead, and now the FocusOut/FocusIn and KeymapNotify events are gone from xev when using ALT.
Thanks, this means that you are right about this not being a bug in wine (I marked it as such now) and that it can be closed, I guess.