Locking issue in message.c

[Emmanuel <e allaud wanadoo fr>]

	Hi all,
There is a locking issue I don't quite understand in message.c : why don't 
we lock the source and destination mailboxes when we copy messages between 
2 mailboxes (in libbalsa_message[s]_copy)? I can't actually imagine a 
scenario where this could be harmful, but I think we should lock them 
while we modify their contents.

Bye
Manu