* string.c (rb_str_inspect): refix r40413, on Ruby 1.9 usual character
  escape uses hex/Unicode escapes, so fix to use Unicode escape on
  Unicode strings and hex on others. [ruby-core:54458] [Bug #8290]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40423 b2dd03c8-39d4-4d8f-98ff-823fe69b080e