* add RUBY_TYPED_FREE_IMMEDIATELY to data types which only use
  safe functions during garbage collection such as xfree().
  On default, T_DATA objects are freed at same points as fianlizers.
  This approach protects issues such as reported by [ruby-dev:35578].
  However, freeing T_DATA objects immediately helps heap usage.
  Most of T_DATA (in other words, most of dfree functions) are safe.
  However, we turned off RUBY_TYPED_FREE_IMMEDIATELY by default
  for safety.
* cont.c: ditto.
* dir.c: ditto.
* encoding.c: ditto.
* enumerator.c: ditto.
* error.c: ditto.
* file.c: ditto.
* gc.c: ditto.
* io.c: ditto.
* iseq.c: ditto.
* marshal.c: ditto.
* parse.y: ditto.
* proc.c: ditto.
* process.c: ditto.
* random.c: ditto.
* thread.c: ditto.
* time.c: ditto.
* transcode.c: ditto.
* variable.c: ditto.
* vm.c: ditto.
* vm_backtrace.c: ditto.
* vm_trace.c: ditto.
* ext/bigdecimal/bigdecimal.c: ditto.
* ext/objspace/objspace.c: ditto.
* ext/stringio/stringio.c: ditto.
* ext/strscan/strscan.c: ditto.



git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@43466 b2dd03c8-39d4-4d8f-98ff-823fe69b080e