The main "connect" and "edit" windows set the "escape-exits" flag, but
that just closed the form without exiting the app, leaving the user
trapped. Fix this by emitting a signal when the form quits, and
catching that. (And now we don't need to watch the "clicked" signal on
the quit buttons, since they have the "exit-on-activate" flag set.)
When activating a never-before-used Wi-Fi network, we need to call
nm_client_add_and_activate_connection(), not
nm_client_activate_connection(). (We still pass a NULL connection,
since NM will attempt to auto-fill it for us, and will succeed as long
as it's not an 802.1x connection.)
We were using g_utf8_strlen() to measure strings for layout, but that
counts combining marks too, and also fails to deal with "fullwidth"
(ie, double-width) CJK characters.
Add a new utility function to do a better job of this (based on code
from vte), and use it everywhere.
