- it disables most 2D drawing in order to favor a fullscreen output view for screenshot taking
- enabling the console or any menu should cancel it
- it does use several CVARs but their state should be restored when this mode is canceled
The main catch is now in D_DoomMain, only calling platform specific functions to handle the output for the error.
As a nice side effect, -norun can now be done without an exception, just by exiting D_DoomMain with a special exit code.
Many had leftover non-default constructors/ assignment operators, and some were initialized, even though the initialized data was never used.
In case of FCycler this even caused a default setting to be overwritten when used inside FDynamicLight.
