The welcome message is displayed using xmessage(1), not using your
terminal. Thus, it makes no sense to have this option anymore. Also,
the new lex/yacc parser cannot correctly handle the situation:
normal variables are expanded before parsing the file. As a replacement,
you can use:
set $terminal /usr/bin/urxvt
Also update documentation (manpage, userguide).
To make the code easier to read/write when checking if a client is
floating, introduce client_is_floating().
Details which are missing: A command to hide/show all floating clients,
moving/resizing clients with your mouse holding Mod1 (click anywhere
in the client, not just on its borders), resize/move by keyboard, select
next/previous client by keyboard
