Pop up a frame to read news.
This will call one of the Gnus commands which is specified by the user
option `gnus-other-frame-function' (default `gnus') with the argument
ARG if Gnus is not running, otherwise just pop up a Gnus frame. The
optional second argument DISPLAY should be a standard display string
such as "unix:0" to specify where to pop up a frame. If DISPLAY is
omitted or the function `make-frame-on-display' is not available, the
current display is used.
(fn &optional ARG DISPLAY)