SF2 and other bit depths

[baconpaul]

@CurlyMC kindly gave me some SF2 files with bit depths other than 16 which don't load

So lets just figure out why. 24 bit wav work so SF2 should be easy

[baconpaul]

OK @CurlyMC I have a change which loads 24 bit SF2 (mono only for now) and also supports SF2 loop points. Will merge it this morning. With that all four of your test SF2 play perfectly fine.

This issue will close when I merge it, so if you self build, you can pull then (don't forget to submodule update). If you use binaries, nightlies run about an hour behind merges.

And I don't know if you use discord, but if you want to do more testing and fun on short circuit, please feel free to hang out in the sc-development channel!