Teach Bundler to recognize mri_22 platform

See e6bc48eb.

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Teach Bundler to recognize (x64_)mingw_22 platform

See e6bc48eb.

Signed-off-by: Alex Coles <alex@alexbcoles.com>
Merge pull request #3328 from myabc/ruby-22-fixes

Ruby 2.2: support mri_22, (x64_)mingw_22 as platform options