Sometimes pulse effects aren't applied [plebitp]

[danfrz]

There's a bug with plebitp where pulse effects will not work properly sometimes. I've noticed it only happens in certain instruments and when it does happen, it happens 50% of the times you play the same segment of the song, which strongly suggests some sort of uninitialized malarkey. This was happening even before the pulse table was introduced.

[danfrz]

Copy constructor for Instrument didn't copy over the pulse index from the old instrument so when an Excerpt of a Song was made the new instruments in that song had uninitialized pulse data and was saved to the playback file. This caused inconsistent playback for pulse-modulated instruments.