Ruby

merge revision(s) 77596fb7a91cc119b25ac9e19b3c8682709765b4: [Backport #16138]

    Do not turn on keyword_init for Struct subclass if keyword hash is
     empty

    This was accidentally turned on because there was no checking for
    Qundef.

    Also, since only a single keyword is currently supported, simplify
    the rb_get_kwargs call.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/branches/ruby_2_5@67866 b2dd03c8-39d4-4d8f-98ff-823fe69b080e