Update User Manual
User Manual for ScummVM was created in 2007 and was not significantly updated since. Many new features got added and existing pages would need to be improved.
Add more Doxygen comments to OSystem
We use doxygen for documenting ScummVM. Unfortunately, we were not very consistent with describing the newly added methods and classes.
Directories to cover:
* common/ * audio/ * backends/ * graphics/ * gui/ * image/ * video/ * engines/*.h (only files in the root directory)