Milter-greylist

I installed milter-greylist into a FreeBSD 4.x box with libbind and
found some problems:

* The pthread library (-lc_r) must be found before others. Otherwise,
libbind refers pthread symbols and everything fails.
* LIBS=$LIBS"-lspf2" -> LIBS="-lfoo-lspf2"
* We need sys/types.h before netinet/in.h.
* NS_MAXMSG is typically 65535. Stack overflow happens.
* When we use newer BerkeleyDB implementation, we include db_185.h
instead of db.h.