Milter-greylist

Hello,

At the end I got a usable core dump to figure out the reason
of the long standing problem of milter-greylist process crash.

In the function sync_waitdata() the value of "fd" is not checked
against of FD_SETSIZE. It must have a value smaller than that.

Please apply the patch attached to that message.

While I was debugging I found code which seemingly left over
(pthread_mutex_(init|lock) on an auto variable in a thread,
which is nowhere else referred to) 
and I could optimize out one member of the struct sync (s_peer).
It is not needed since each peer has his own private sync list.

Best,
Attila