* change the license of the main file because there is no more id-based code here licensed under the GPL.
* moved VM interface definition out of the implementation.
* moved idmus CCMD out of implementation because it is dependent on Doom level definitions.
* moved s_music.cpp into the music folder with the rest of the music code.
These were creating dangerous interdependencies. It is better to do explicit conversions when needed.
As an added plus, this means that zstring.h no longer depends on name.h which was very annoying.
- 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.
