Prepare for release 2.3.0.
Add new $dmenu_bottom spawn argument variable for use with dmenu.
Evaluates to '-b' if bar_at_bottom is enabled.

Change default dmenu spawns to include $dmenu_bottom.
Revert "Automatically adjust internal dmenu args when bar_at_bottom is set."

Implemented differently upstream.
Merge remote-tracking branch 'origin/master'
Update fork status.