* gc.c (rb_gc_mark_values): added.
  This function is similar to rb_gc_mark_locations(), but not
  conservertive.
* internal.h: ditto.
* vm.c (env_mark): use rb_gc_mark_values() because env values should
  be Ruby VALUEs.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@47533 b2dd03c8-39d4-4d8f-98ff-823fe69b080e