Main change is that we now close X11 display on program exit: as this couldn't

Main change is that we now close X11 display on program exit: as this couldn't
be done in wxApp dtor (too early), a special module had to be created for it
and module dependencies added for the other modules which have to be cleaned
up while the display is still open.

Also a few minor formatting changes and removed a couple of unused variables
from wxApp.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@42119 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775