Update mail/spamass-milter to 0.4.0.

Brief summary of changes (taken from upstream release announcement):

• -C option to change the default reject code
• -S option to specify a path to sendmail (for the -x option)
• -R option to specify the rejection message
• -a option to skip messages that were authenticated
• IPv6 address support
• zombie process fix for the - option introduced in 0.3.2

Some of these changes (notably the -R and -a flags and the IPv6
support) were previously included in the port via patch files, which
are now unneeded and have been removed.