add support for playback of custom key signature
I created a score with a custom key signature (with B flattened and C sharpened) and entered three notes: A, B(b), C(#).
It displayed correctly, as A, Bb, C#.
I played the score.
It played A, B, C, as if no key signature had been added.
I changed the key signature to F major (which also has a flattened B).
It incorrectly added a natural in front of the B, and did nothing to the C.
Again, it was acting as if there had been no key signature there previously.
I've attached a test score with the fault.
This bug occurred on version 0.9.6 RC1 (revision 3070) and also on the latest revision 3085.
I'm running windows vista.