Test needed to check if multi-words are superfluous

[luzpaz]

There are many examples of multi word entries that aren't necessary:

aall of->all of is rendered useless if the word aall->all is already in the dictionary
or
confirmed bby->confirmed by when bby->by is already present.

But there are some usecases when this is necessary like a frequent grammatical mistake better then->better than. Now even though better then is a valid assertion, I think that in most contexts, this will be an error.