Fixed multiple newly discovered issues:

1.  Putting sample in index 1, and then 3, caused a SEGFAULT because the
placement (relative vs. indexed) was being confused.  How this went
undetected for almost 2 months I have no idea.

2.  Memory leak on sample loading.  Should also be a hell of a lot faster
now.

TODO:  2 instances of the same sample can't be played on the same note...
Not catastrophic, but there are use-cases for that.