marshal.c: do not recycle wrapper objects

* marshal.c (marshal_dump, marshal_load): do not recycle wrapper
  objects, to prevent from segfault with continuation.
  [ruby-dev:47970] [Bug #9523]

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@45025 b2dd03c8-39d4-4d8f-98ff-823fe69b080e