Attempt to locate source of crash when resizing video clients.

Intermediate commit, contains a lot of debug output,
duplicate/unnecessary code and other ugly things you do not want to see
when you're alone in the dark.
Track down mplayer resize issue.

... turns out to be a division by zero. If I think about it, I even
think this generally makes floating applications crash.

mplayer still refuses to enter fullscreen mode.
Prepare to merge into master.

Clean up unneeded debug messages, correct some grammar mistakes in the
README.
Merge branch 'fullscreen'.

A fix for the crashing WM when attempting to resize a fullscreen
application. VLC now correctly enters fullscreen, mplayer however
behaves weirdly (upon toggling fullscreen, the window gets unmapped and
remapped, but as far as I interpret the window's properties, nothing
tells me to treat it as fullscreen.

Anyway, this gets merged already now, just for the sake of fixing the
crash issue.