* string.c (rb_str_new_frozen): refactoring code.
  * Move code from str_new_frozen_with_klass() (and remove it)
  * `aux.shared' should not be 0 for STR_SHARED strings.



git-svn-id: svn+ssh://svn.ruby-lang.org/ruby/trunk@44822 b2dd03c8-39d4-4d8f-98ff-823fe69b080e