Minimize typing output in the case where suffix is encoded as a new entry in the dictionary.

Minimize typing output in the case where suffix is encoded as a new entry in the dictionary.

For example:
S: "drive"
S/S: "driving"

Before this change plover would backspace 6 (drive plus the space before it) then type " driving". WIth this change it will only backspace one char and then type "ing".

Plover used to do this but a recent refactoring caused this regression. Now it does it properly again.