Add support for more MOD channel formats

[DevanWolf]

The player is missing some multichannel magic, so without it for example the player won't load MOD files with 16 channels but instead load as 4 channel. This change/update I have made will support it. (Includes "xxxC" for 100-999 channel MODs that are made using TuComposer or a future version of OpenMPT)