Move to bugzilla 2.20

Move to bugzilla 2.20
From the release-notes.html:

What's New?
 New User-Interface Color/Style
 Higher-Level Categorization of Bugs (above "Product")
 Regular Reports by Email of Complex Queries ("Whining")
 "Environment Variable" Authentication Method
 User-List Drop-Down Menus
 Server-Side Comment Wrapping
 UI for Editing Priority, OS, Platform, and Severity
 Bugzilla Queries as RSS
 Choice of E-Mail Sending Methods
 "Large Attachment" Storage
 and lots of Miscellaneous Improvements

See http://www.bugzilla.org/releases/2.20/release-notes.html for
all the details.