(PUP-2777) Bundler Windows x64 workflow

 - Ensure that Bundler loads proper gemset whether on x86 or x64, based
   on what is defined in project_data.yaml
 - Note that latest FFI compatible gems have been added to x64 out of
   necessity, but the code fails tests, and is not yet compatible with
   Ruby 2 changes / gem updates.
 - Gem versions for Ruby 1.9.x were kept the same, and will be upgraded
   as part of verifying gem compatibility when updating 1.9.x branch
   to use latest FFI compatible gems.
After reviewing this more, I don't think that `x64_platform` resolves to what you think it might.