Ruby » Ruby master

merge revision(s) 39967: [Backport #8194]

    * time.c (num_exact): use to_r method only if to_int method is
      available.
      [ruby-core:53764] [Bug #8173] reported by Hiro Asari.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_1_9_3@40054 b2dd03c8-39d4-4d8f-98ff-823fe69b080e