* string.c (enc_strlen): move UTF-8 optimization from str_strlen to
  enc_strlen.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45617 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* string.c (str_strlen): use enc_strlen if the coderange is known.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45618 b2dd03c8-39d4-4d8f-98ff-823fe69b080e