merge revision(s) 54721: [Backport #12311]
* ext/date/date_core.c (Init_date_core): [DOC] Convert DateTime documentation to RDoc from Markdown. [ruby-core:75136] [Bug #12311]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@55358 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 54721: [Backport #12311]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@55358 b2dd03c8-39d4-4d8f-98ff-823fe69b080e