Add Interval backsteps input cursor

When you add an interval to a chord (instead of adding "named" notes) the input cursor rewinds to before the active note, making the next note entry overwrite the current.

Steps to reproduce:

1. Enter a C (high c, in the staff), and press Shift+G to add a G to the chord. Observe that the input cursor stays to the right side of the chord.
2. Add a D (fourth below the G) by pressing Shift+4.

Expected behaviour: The D is added, and the cursor stays on the right side of the chord.
Actual behaviour: The D is added, and the cursor moves to the left of the chord. If you enter a new note at this point, the chord is overwritten.

(tested with r2006, winXP)