man: add stub sd-bus(3) We have 126 broken links to sd-bus.html, it's nice to fix that. Current version is mostly a stub, with a long list of links to other pages. I think that's fine, especially that sd-bus might evolve quite a bit before it is made public. Not all of linked pages are written. Still missing: sd_bus_can_send sd_bus_get_name_creds sd_bus_get_owner_creds sd_bus_message_can_send sd_bus_message_get_creds sd_bus_message_set_allow_interactive_authorization sd_bus_send sd_bus_set_address sd_bus_set_description sd_bus_start sd_event_set_prepare sd-device systemd.busname