Moved DPD signatures into script specific directories.

 - This caused us to lose signatures for POP3 and Bittorrent.  These will
   need discovered in the repository again when we add scripts
   for those analyzers.
Fix a bug where the same analyzer tag was reused for two different analyzers.
Added a missing curly brace in smtp/dpd.sig
Small test fixes.
const adjustment

And fixes compiler warning about overloaded virtual function hiding.
Merge remote-tracking branch 'origin/fastpath'

* origin/fastpath:
  const adjustment
Merge remote-tracking branch 'origin/topic/seth/bittorrent-fix-and-dpd-sig-breakout'

Closes #1035.

* origin/topic/seth/bittorrent-fix-and-dpd-sig-breakout:
  Small test fixes.
  Added a missing curly brace in smtp/dpd.sig
  Fix a bug where the same analyzer tag was reused for two different analyzers.
  Moved DPD signatures into script specific directories.
Bringing the DPD POP3 signature back.

This also avoids the need for updating the external test suite.