Do not mute note when setting new instrument

When changing the instrument while a note is playing the attack sequence of the
instrument is played again.
Cleanup sample
Cleanup whitespace
Resample to 44100Hz
Add end command
Add SDL context reset function

Also correct interpreter reset function.
Implement pause sound

Pause sound is played when file is paused in interactive mode.
When option `u` is given at startup the pause sound will not be played.
Remove whitespace
Merge branch '0.4' into drum-n-bass.blip