[#42296389] Added support for lucid in rbenv pkg and rbenv-ruby 1.9.3 pkg

This commit does the following:

* Updating changelog for rbenv for lucid support
* Updating changelog for rbenv-ruby-1.9.3-p392 for lucid support
* Changed debian/compact for rbenv-ruby-1.9.3-p392 to 7 as lucid
  currently doesnt support debhelper version 8. Also updated
  debian/control for debhelper version (as build dependant of ruby)

Waiting for launchpad to build packages. Dont merge till then