move fields to ec.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59195 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
move fields to ec.
to rb_execution_context_t.
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@59195 b2dd03c8-39d4-4d8f-98ff-823fe69b080e