[ticket/12393] Properly disable edit buttons' quickedit event during quickedit

This change will make sure that clicking the quickedit buttons while a
quickedit is in progress will not cause an AJAX request.

PHPBB3-12393
[ticket/12393] Open quickedit window whenever edit is clicked on post

This will be another slight change in behavior. When clicking the edit button
on a post the quickedit window will appear. Clicking the edit button of a
different post will cancel the initial quickedit and open another quickedit
window in the post the edit button was clicked in instead of going to the
full editor as introduced by the previous commit.

PHPBB3-12393