Also update documentation (manpage, userguide).
To make the code easier to read/write when checking if a client is
floating, introduce client_is_floating().
However, it is a bit more flexible obviously. You can specify the
offset of the window you want to go to, to implement workflows like
the following:
* Jump to mutt
* Jump to irssi
* Jump back ("focus 2" would be the command)
Michael Stapelberg