Log Message:
Take maintainership.  Update to bogofilter-0.17.5.

Changes:
* Change default parameters to the results of Greg's 300k ham
  and 300k spam bogotune run:

	     robs     robx    min_dev  spam_co
      old  0.010000 0.415000 0.100000 0.950000
      new  0.017800 0.520000 0.375000 0.990000
* Fix check for PGP signatures.
* Ignore data portion of PGP signatures.
* Use "mime:" (rather than "head:") to tag mime part headers.
* Fix "Can't find '.MSG_COUNT'" problem in bogotune.
* Fix defect that continues decoding base64/qp after invalid chars.
* Warn if user specified config file doesn't exist.
* Fix tagging of IPAddrs in header lines.
* Fixed minor bogotune problems related to building wordlists.
* Exempt tokens .MSG_COUNT and .ROBX from maintenance operations.
* Remove unused 'active' and 'weight' attributes of wordlists.
* If message uses CRLF, put CRLF after added header lines.
* Removed DEPRECATED CODE.
* Correct SIGSEGV causes by missing environment variables.
* Miscellaneous Portability fixes
* Documentation cleanups.