+ Allow users to say why they edited a post

Signed-off-by: Michael Eshom <oldiesmann@oldiesmann.us>
Merge branch 'release-2.1' of https://github.com/SimpleMachines/SMF2.1 into pm_labels
Merge pull request #873 from Oldiesmann/pm_labels

+ Allow users to say why they edited a post (full edit only at the moment)