Unedited parts of misspelled regions are still considered misspelled

To reproduce: with spell checking on, type "goood", then delete an o, then click in front of the literal and ask for the next misspelled word.

If people are using spell checking, and using the suggestions dialog to replace misspellings, this doesn't crop up (since overwrite is really a delete and insert, and the current misspelling region tracking removes sub-parts of regions corresponding to deletions). And even if an occasional manual edit left extra regions, that just makes the ui slightly less efficient to use.

So this seems very low priority, but this filing lets people know it's a known problem in case anyone else comes across it.

Start by reproducing the spell-checking case: type "goood", delete an "o", then request the next misspelled word from before the literal. Trace the misspelling-region tracking around that deletion; the fix is done when the unedited remainder is no longer reported as misspelled.