gnu: guile-wm and guile-xcb: Build with guile-2.2.

* gnu/packages/guile-wm.scm (guile-wm): Build with guile-2.2.
(arguments)[configure-flags]: Replace references of "2.0" with "2.2".
(inputs): Use guile-2.2.
* (guile-xcb): Build with guile-2.2.
(arguments)[configure-flags] Use Guile 2.2.

Signed-off-by: Kei Kebreau <kkebreau@posteo.net>