* doc/extension.ja.rdoc: removed rendering error caused by editor specific
configuration on http://docs.ruby-lang.org/en/trunk/extension_rdoc.html .
[Bug #12111][ruby-core:73990]
* doc/extension.rdoc, doc/extension.ja.rdoc: add editor local
variables, with commenting out by :enddoc: directives which are
just ignored unless code object mode. [Bug #12111]
merge revision(s) 53947,53948: [Backport #12111]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_3@54409 b2dd03c8-39d4-4d8f-98ff-823fe69b080e