Milter-greylist

Hi,

I've made a few modifications in order to make milter-greylist perform
more responsive and faster at bigger loads:

      * Bucketed search of autowhitelisted and pending entries rather
        than write-locked only-one-at-the-time full list search
      * Large buffer for writing the dumpfile (10M)
      * New option line for the greylist.conf that allows you to disable
        the comment at the end of each dumpfile line. Apparently
        formating the date and time is quite time/cpu consumable task -
        especially if you have to do it a few hundred thousand times in
        a row. The config file option is 'dump_no_time_translation'.

...and a fix to what I consider to be a bug:
      * 'mxsync' client connection is set non-blocking, but there were
        no checks if fprintf() actually delivers the complete sync
        message to the peer or just the part of it.
      * Also, when reading the 'mxsync' client connection, being non-
        blocking, fgets() can bail out with NULL and EAGAIN which is not
        fatal error for the connection.

Best regards,

Ranko