How to make ruby-debug work in Ruby 1.9.3

An alternative that will make ruby-debug, perftools.rb and some other tools work without installing pre-release versions is to use a tiny patch that re-exposes the _ruby_current_thread symbol.

https://github.com/ruby/ruby/pull/47

Here's a script to install ruby-1.9.3-p0 with the patch applied using ruby-build: https://gist.github.com/1270704