Enable P4-Ruby to compile and test with Ruby 1.9.
The current solution is far from ideal because it is not possible to compile
and test both Ruby 1.8 and Ruby 1.9 in parallel. The Makefile writes both
artifacts and binaries to the same location.
This means a user/tester/builder needs to choose on Ruby platform or ensure
'make clean' is called first.
Many of the test cases also still fail in Ruby 1.9. We also need to investigate
the Unicode story with Ruby 1.9 and see if the lessons learned from Python 3
can be applied somehow.