Fixes this cppcheck finding:
[nx-X11/programs/Xserver/xkb/xkbActions.c:1306]: (error) Uninitialized variable: oldState

  commit 35a4b8e7f4526a92d44cb16a783f21030cd1f6df
  Author: Peter Hutterer <peter.hutterer@who-t.net>
  Date:   Tue May 5 16:51:59 2009 +1000

    xkb: remove oldState from XkbHandleActions.

    I really don't know what the purpose of this variable is or was, aside from
    potentially clobbering up our key state since there's a path where it may be
    used uninitialised.

    Also, this means that xkbi->prev_state is now accessible from the DIX with
    meaningful data.
Signed-off-by: Peter Hutterer <peter.hutterer@who-t.net>