Add Loop Amount

[Enverex]

Currently you can set whether looping is enabled or not, but this obviously doesn't work when converting as it'll just loop forever and create a file of infinite size.

Would it be possible to add a loop amount option? e.g. "-l 2" so that it loops twice then ends.

I should clarify that this should be for modules that explicitly have a loop point and would normally loop during playback, not just general looping of tracks.

[AliceLR]

libxmp doesn't distinguish between looping at module end and looping from a jump, so this change will affect both.