test_tracepoint.rb: include zombies

* test/-ext-/tracepoint/test_tracepoint.rb (test_tracks_objspace_count):
  free count should include zombies.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43209 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
string.c: mark frozen string

* string.c (rb_fstring): because of lazy sweep, str may be unmaked
  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