"Furthermore, since there is not a one-to-one correspondence between
threads and connections (N connections mapped onto M threads,
M <= N), connection-specific data must be accessed through the handles
provided by the Milter library."
which in other words means php_request_startup() and the corresponding
php_request_shutdown() will never be called for the same thread
reopen file per request, so milter doesn't hang. PHPA or APC can be used to speed the milter up
added a milter_init callback to init the milter before it is registered
added protos to make sniper happy