This should have no user-visible impact.
For vim `.` to repeat it's important that actions are replayable.
Currently editor::MoveDown *sometimes* moves the cursor down, and
*sometimes* selects the next completion.
For replay we need to be able to separate the two.
After #2641 we noticed that scrolling didn't take a count parameter.
The PageDown/PageUp logic was also broken by an additional -1 (for both
vim mode and not).
Conrad Irwin
Kay Simmons