* numeric.c (num_quo): Use to_r method to convert the receiver to
  rational.  [ruby-core:41575] [Bug #5736]

* test/ruby/test_numeric.rb: add a test for the above change.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@41109 b2dd03c8-39d4-4d8f-98ff-823fe69b080e