[game clients] Avoid hitting the database twice when possible
[game clients] Always disable incompatible game client DLLs. No more silent errors with 64-bit game clients on 32-bit systems.
[game clients] Properly initialize "allow VFS" and "require ZIP" configuration parameters for game clients.
[game clients/test] Added test cases for GameFileLoader
[game clients] Avoid extra cast by using aliased variable
[game clients] Avoid passing the game client a nonexistent system directory
[mygames] Fixed: MAME games weren't being shown in MyGames window

XBMC downloads a list of supported extensions from the remote add-ons repo. Zip files are treated as directories and scanned recursively; if they don't contain valid extensions (such as MAME arcade games), the entire zip will be missing from the MyGames window. Skipping the recursive scan always shows zip files (note: entering the zip will show an empty folder) and speeds up directory listing as a nice side effect.
Game client system directories: rename setting to "hassystemdirectory"