circular require warning from RubyGems maven extension

From jruby 1.7.0.dev, circular require is warned in 1.9 mode like CRuby 1.9. And our RubyGems maven extension causes warnings by circular require.

I patched RubyGems at 409c61fb5dace5fc7b532bd78e7d7b4c2ed1bb61 but it modifies RubyGems itself which would make RubyGems update harder.

The requirements are;

• we want to load maven_gemify.rb only if spec_fetcher is required (SpecFetcher is defined by autoload).
• we need to load maven_gemify.rb after spec_fetcher and remote_fetcher to override those definitions.

We should find a way to do above before 1.7.0 GA. I'll try it once RubyGems is updated.