Use a similar detection mechanism to pass itself.

On wayland use:

* dmenu-wl instead of dmenu, an (almost) drop-in replacement
* ydotool instead of xdotool, a uinput-based replacement for
  xdotool. It is not as feature-complete, but probably the
  simplest (or only?) way to add the --type functionality to
  passmenu on wayland.

If IFS (Input Field Separator) is not emptied, read will actually strip
spaces and tabs at the beginning/end end of the "line".

Prof. Aho always seemed neat, but parsing a script inside a script for
the simple purpose of removing the trailing new line seems a bit absurd.
So, instead use two processes! One for getting the first line and one
for removing the trailing line. Everybody loves more calls to fork(),
right?

It seems this file doesn't use spaces any more.