Instead of connecting to the needed tag-update-signal again for every layoutbox,
this now just creates a single connection and updates all layoutboxes from here.
A new weak table is used to find the layoutboxes from these callbacks.
Additionally, layoutboxes are now per-screen unique. So even if you try to
create three layoutboxes for screen 1, the code will now always return the same
instance.
This kind-of fixes the leak test for layoutboxes. The problem is that the
default config also creates a layoutbox and adds it to a wibox. Since this is
now the same layoutbox, the test still fails. Just removing the layoutbox-part
from the default config makes this problem go away.
Signed-off-by: Uli Schlachter <psychon@znc.in>
6f2e7bba25