Here is a re-working of the winbindd

Here is a re-working of the winbindd
reconnect code to cope with rebooting a DC. This
replaces the code I asked Volker to revert.
The logic is pretty simple. It adds a new parameter,
"winbind reconnect delay", set to 30 seconds by
default, which determines how long to wait between
connection attempts.
To avoid overwhelming the box with DC-probe
forked children, the code now keeps track of
the DC probe child per winbindd_domain struct
and only starts a new one if the existing one
has died.
I also added a little logic to make sure the
dc probe child always sends a message whatever
the reason for exit so we will always reschedule
another connect attempt.
Also added documentation.
Jeremy.
(This used to be commit 8027197635b988b3dcf9d3d00126a024e768fa62)