merge revision(s) 57758: [Backport #13268]
string.c: restore documentation for String#<< * string.c: [DOC] restore documentation for String#<< which became undocumented with r56021; fix a typo. [ruby-core:79865] [Bug #13268]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@57919 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
merge revision(s) 57758: [Backport #13268]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_4@57919 b2dd03c8-39d4-4d8f-98ff-823fe69b080e