Fix issues relating to SDL and wxWidgets interaction in Atlas.
This fixes the transfer of key inputs from WxWidgets to SDL, making it possible to type in the in-game GUI from Atlas.
Also fixes whitespace issues in some Atlas files.
The following improvements are OSX specific:
- fixes an SDL assertion related to unused subsystems in Atlas.
- Remove the 'osxguiapplication' override. This fixes the editor starting up in the background and not accepting input when launched from in-game.
- To prevent an issue with sdl/wxwidgets conflict when running from inside the game, actually boot a new instance (see #2427)
Reported by: wik (Many thanks for your investigations)
Tested by: trompetin17, Stan
Differential Revision: https://code.wildfiregames.com/D2788