Assert SMFIF capabilities so that LUA odkim.add_rcpt, odkim.del_rcpt, odkim.del_header and odkim.quarantine actually work

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The LUA final policy script functions odkim.add_rcpt, odkim.del_rcpt, odkim.del_header and odkim.quarantine need some Milter capability flags to be set (respectivley: SMFIF_ADDRCPT, SMFIF_DELRCPT, SMFIF_CHGHDRS and SMFIF_QUARANTINE), but these capabilities are not always activated depending on OpenDKIM configuration parameters.

This patch enforces activation of these capabilities if FinalPolicyScript is defined in opendkim.conf, so that related functions actually work regardless of other configuration parameters.