This eliminates another piece of hideous code.
This commit also moves the memory error handler to the common code, so that all games can call it if triggered.
* removed some redundant functionality (e.g. Shift-F5 to change - use the console for that!)
* removed a few more leftover parts of the old music system
* savegames should not do more than resuming the music at the point of saving. (DN3D and RR only so far. Blood to be done.)
* handle music enabling/disabling in the backend, which simply knows better what to do. This was only working in the menu, so changing the CVAR had no effect.
* implemented single image screens
* implemented skeleton of the image scroller
* added RR-specific definitions to the menus (need to copy and adjust d_menu.cpp)
* added definitions for credits screens.
Unfortunately this means that the keybinding menus in all games except Blood are shot to shit right now because of how they passed the data on to its destination.
These menus are not fixable, this will have to wait until the replacement is up.
* moved the binding commands to osd.cpp. They were in the global namespace already and this way everything to be tossed out is in the same place when the time comes.
* removed support for the OSDs native CVARs. The only ones left were some internal ones I won't need until this code can be replaced.
* same for the custpmization code the games added. Duke Nukem was the only one anyway to have a decent font for it.
* saving of demos and savegames no longer mindlessly writes to the mod directory. All such access is now being rerouted through the special paths interface so that the game data can reside in write protected locations.
* refactored all occurences of klistpath except fnlist_getnames.
* do not allow CON scripts to write to arbitrary files. This is a massive exploit and can be used to cause real damage if someone knows how to play this thing - it's far easier than people may think! It will now write any such data to a special section in the main config which is safe and cannot be manipulated to write to random locations on the hard drive.
Some part are not done yet, and the file system data is currently ignored - there's no way to properly set this up with the file system code Build came with.
Having this grouped in a single object will make refactoring a lot easier.
Access functions have been provided to avoid changing client code for the reorganization.
