Add 'name' argument to weston_output_init(). This is much more obvious
than the assert inside weston_output_init() to ensure the caller has set
a field in weston_output first.

Now weston_output_init() will strdup() the name itself, which means we
can drop a whole bunch of strdup()s in the backends. This matches
weston_output_destroy() which was already calling free() on the name.

All backends are slightly reordered to call weston_output_init() before
accessing any fields of weston_output, except the Wayland backend which
would make it a little awkward to do it in this patch. Mind, that
weston_output_init() still does not reset the struct to zero - it is
presumed the caller has done it, since weston_output is embedded in the
backend output structs.

Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>
Reviewed-by: Ian Ray <ian.ray@ge.com>
Reviewed-by: David Fort <contact@hardening-consulting.com>
[Daniel: document name copying]
Acked-by Daniel Stone <daniels@collabora.com>