Two new ways of changing range:
- Press Z to snap to cursors, or M to open a dialog and enter manually.
- The frequency boxes now scroll in a more sane way - round down to the
nearest multiple of 10, then divide by 10 to find out the increment.
For example, at 2kHz, the next value will be 2.1kHz (2000 + 1000/10)
rather than 2.001Hz (2000 + 1).
Former-commit-id: 80b928cc27