In some places, both JIT and MJIT are being used, but it could be
confusing for new comers. We're not explaining MJIT on NEWS file or release
notes as well. So we consider MJIT as an internal term of implementation
like YARV.

configure.ac: ditto

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@65810 b2dd03c8-39d4-4d8f-98ff-823fe69b080e