Add native function sexypsfsetinfiniteloop(bool) to tell the sexypsf if it should use infinite loop.
Note:
1) Currently it is for psf, psf2 is not affected;
2) It works on the songs that loop, but will get silence after end for the songs that don't loop;
A way to fix 2) is to let it end (maybe check some loop flag? or when it get silence for a few seconds.)
Use another approach for infinite loop:
1) Set a global flag;
2) In spu.c, check the flag and go with the loop, it works for songs that loop;
3) For the songs that does not loop, check the samples, if it's silence for a few seconds, consider it ends and let it end;
4) For the songs that loop, it will know it's not silence in the checking, and if it's not silence for like 15 seconds, consider it a loop song, and don't check silence anymore.
For now it works well.
Merge branch 'DEV_infinite_loop'
Version 1.2.2
Support native loop feature for PSF.
  For songs that natively loop, it works well;
  For songs that do not loop, it checks silence for a few seconds, and restart the song if it ends.

Note: PSF2 loop is not supported yet.