rational.c: ensure to be Rational
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42178 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
rational.c: ensure to be Rational
Rational#*, but mathn.rb breaks that assumption. [ruby-core:56177]
[Bug #8687]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@42178 b2dd03c8-39d4-4d8f-98ff-823fe69b080e