ghash: Document order of parameters in GEqualFunc usage
ghash: Document order of parameters in GEqualFunc usage

See https://bugzilla.gnome.org/show_bug.cgi?id=698064#c15.

johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,johne53/MB3Glib,endlessm/glib,endlessm/glib,endlessm/glib