pack tonTyp struct

[ftrvxmtrx]

Code throughout seem to expect sizeof(tonTyp) to be exactly 5 bytes, which is the case if gcc is used, but, while porting to Plan 9, it was found that sizeof is 8 bytes with some compilers instead, resulting in either crashes on loading a module, or incorrect playback.

[8bitbubsy]

Interesting, I thought this would be safe because it consists of bytes only. I made my own commit because I wanted to add some comments and rearrange some stuff in ft2_replayer.h Thanks for pointing out this issue!