I've convinced myself that nothing in DaemonStatus can deadlock,
as it always keepts the TMVar full. That was the only reason it was in the
Annex monad.
This should fix OSX/BSD issues with not noticing transfer information
files with kqueue. Now that threads are used, the thread can manage the
transfer slot allocation and deallocation by itself; much cleaner.
There's still a bug; if the child updates its transfer info file,
then the data from it will superscede the TransferInfo, losing the
info that we should wait on this child.
Added knownRemotes to DaemonStatus. This list is not entirely trivial to
calculate, and having it here should make it easier to add/remove remotes
on the fly later on. It did require plumbing the daemonstatus through to
some more threads.
