Colors taken from dwm's config.default.h and hard-coded in Operations instead
of Config because of import cycle.
Windows overlap slightly in the current tiling algorithm and sometimes prevent
the active window from being completely surrounded by a red border.
This change makes the window under the mouse pointer the focused window. This
isn't quite what we want, but it is a step in the right direction. The next
step is to somehow inhibit the CrossingEvents generated during workspace and
layout switches.
