docs: Clarify the thread-default GMainContext where the result is sent
docs: Clarify the thread-default GMainContext where the result is sent

https://bugzilla.gnome.org/show_bug.cgi?id=783825

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