* reverb/echo is not yet implemented, so there's two stub functions for now.
* RTS needs to be done differently, because the sound engine cannot play raw buffers without any control data.
It's still not active but now should produce correct results when working inside the file system.
What it is missing is a file scanner that picks the data it needs to process.
- disabled the user maps menu because it is hopelessly dependent on functionality that cannot be fixed. Better wait until the menu refactor to do it right - it'd be a waste of time fixing the current menus.
* reroute several error conditions to I_Error.
* removed some soon-to-be obsolete GRP loading code.
* explicitly trigger the SetDefaults script events which depended on side effects from the config implementation.
* removed the nonsensical file system switch. All this does is create instabilities because it is non-obvious from where data is loaded. If a resource is mounted, it should be checked for content no matter what. While this may affect the stray weird mod out there it is a necessity if we want to allow transparent project repackaging.
