rational.c: fix rdoc
* rational.c: [DOC] fix wrong indentations and comment out some lines
in code examples to make them valid Ruby code and syntax highlighted
on the rendered page.
[ci skip] [ruby-core:79607] [Bug #13233]
Author: Marcus Stollsteimer <sto.mar@web.de>
merge revision(s) 57686: [Backport #13233]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@58121 b2dd03c8-39d4-4d8f-98ff-823fe69b080e