string.c: mark frozen string
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43210 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: mark frozen string
already and swept at next time, so mark it for the time being.
[ruby-core:57756]
git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43210 b2dd03c8-39d4-4d8f-98ff-823fe69b080e