When I added support for propose dimensions, I was foolishly just
choosing the min (or max) if only one was set. However, a lot of windows
will a set a very small min size with no max, which meant we would have
really tiny windows when first floating one. The fix was to try set to
75% but then clamp to the min/max dimensions the window gave.
After fixing that, there was still an issue where windows kept their
size after being floated. That's because there was a propose_dimensions
call happening later in Window.manage(). I'm skipping that now if a
window became floating in the same manage event.
76f292332b