use left arrow cursor
Now supports the _NET_WM_STATE_FULLSCREEN protocol

Fullscreen windows are at the same level as dialog windows, i.e., on top of normal windows
doc-string indentation
Move window fullscreening to policy-simple.rkt to have it also for stacking. However it does not yet support unmaximizing (requires to remember the old position, which asks for a mechanism to remember any kinds of properties of windows.
fix condition
clean up text
transient_for is now recognized as a window to place above tiling