[DRE-maint] Bug#791771: ruby-bdb: FTBFS; dead upstream

[Christian Hofstaedtler]

Package: ruby-bdb
Version: 0.6.6-1
Severity: serious
Justification: fails to build from source (but built successfully in the past)

ruby-bdb currently FTBFS with ruby2.2, and only built on 2.1 due to
numerous patches. It's also dead upstream.

I believe we should remove it (as other distros already did).

Christian