BUGS
* collapsed clients outside stacked mode don't always uncollapse when they receive focus
* resizing within a column affects clients it shouldn't (seems to average client size?)
* geometry goes wacky with lots of clients in one column
* various qiv brokenness
* dosbox won't grab the mouse

4.0
* Opaque managed moves. I know I've argued against it, but it may be doable.
* Regex-based tag strings
* Resizable managed area
* Grow and shrink ctl commands
* New dmenu, with real cursor; snarfable.