#2837 Missing documentation for wm attributes -type

[Colin McDonald]

X Window Extended Window Manager Hints were added
as the wm attributes -type option in Tip 359
This has not been documented in the wm man page.

A list of possible values could be adapted from the
_NET_WM_WINDOW_TYPE section of
http://standards.freedesktop.org/wm-spec/wm-spec-latest.html