String#uminus dedupes unconditionally
String#uminus dedupes unconditionally

[Feature #14478] [ruby-core:85669]

Thanks-to: Sam Saffron <sam.saffron@gmail.com>

git-svn-id: ab86ecd26fe50a6a239cacb71380e346f71cee7d@63566 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

ruby/spec,ruby/spec,ruby/rubyspec,eregon/rubyspec,ruby/spec,ruby/rubyspec,nobu/rubyspec,eregon/rubyspec,nobu/rubyspec,nobu/rubyspec,eregon/rubyspec