merge revision(s) 50509: [Backport #11132]
* string.c: added documentation for character sequence \' with String#sub [Bug #11132][ruby-core:69121][fix GH-900][ci skip] Patch by @shishir127
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@50628 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 50509: [Backport #11132]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_2@50628 b2dd03c8-39d4-4d8f-98ff-823fe69b080e