The following patch changes roundup 1.4.19 to provide a new db.txSource
parameter that has one of 4 values currently:

  unset - reported when using a script/roundup-admin
  cgi - reported when using any web based technique
  email - reported when using any email based technique
  email/pgp - reported when email based technique uses pgp signed emails
 
The detector (to be attached) can be used to test the code.

Currently it has been tested with standard email (not pgp signed)
and the stand alone web server (using the demo.py mechanism).

As it stands I claim it can be rolled into a release with a note to
see this ticket for it's current testing status. It doesn't change
any current functionality so it should be safe for deployment.

It should be tested:
   to report email/pgp for pgp signed emails
   against postgresql or mysql database with multiple overlapping
      transactions via different methods to verify that each issue
      maintains the same txSource through the detectors.