Adjust type in arrays to save unused space

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Refactor vibrato code

Keep sine vibrato as a table, and generate other waveforms in code.
Note: S3M/IT square wave has a minimum value of 0 while MOD/XM doesn't,
but we're using the S3M waveform for everyone.

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>
Update changelog

Signed-off-by: Claudio Matsuoka <cmatsuoka@gmail.com>