":" or "@". (Amazingly, this was not documented before).
* Say that the "nfs" inference is deprecated. (It was deprecated in
revision 1.87 of mount.c, dated 2009-01-11.)
* Add "-t nfs" in an example, so as not to rely on the automatic
inference of nfs when the path contains a colon.
* Try to improve the description of how the arguments are interpreted.