Without having to resort to weird custom defaults.
* Split the current margins setting in three:
* Horizontal margins (because you generally want those two to be balanced).
* Top margin & Bottom margin (because you may want to tweak those separately to deal with quirky status bar/final line shenanigans).
* Also, add a "Reclaim bar height from bottom margin" toggle to the status bar menu, to optionally make sure the status bar won't eat into the bottom margin.
* Includes a free fix to diacritics popup refresh handling in the keyboard ;).
