Log Message:
Update mail/offlineimap to 4.0.16

Added dependency on python curse libraries, do that it does not fail at runtime

Changelog contains many bugfixes, and:
   * Support IPv6 with SSL.
   * improve performance with large folders.
   * new homepage
   * sync INTERNALDATEs.
   * Fixed a bug that could cause OfflineIMAP to crash when copying
     a message from a remote server that didn't have an
     INTERNALDATE.