Explicitly differentiate between rule match and no match

This allows having A -> B, AltrGr+A -> A type of rules where latter
would not work since (AltrGr+)A was compared to A, no difference
found and thus ignored, and then the browser default behavior would
activate we would not get the expected output.

This fixed input from numerical keypad, because we no longer
consume AltGr/Alt input unconditionally.

See https://bugzilla.wikimedia.org/54646
Merge pull request #312 from Nikerabbit/consuming

Given that it's complicated for all of us in the team to test it, we'll deploy it on translatewiki.net and we'll ask the user who opened the bug to test.