copied added ruby 2.1.0 support by replicating code used for ruby 2.0.0 support

with those changes and the changes on https://github.com/cldwalker/debugger-ruby_core_source/pull/29 you can get the debugger compiling and running the tests on ruby 2.1.0 with the same failures we already have running them against ruby 2.0.0 as pointed out on #110.