revert r40760

* vm.c (vm_invoke_proc): revert r40760 partially, which causes timeout
  in test/ruby/test_thread.rb:test_stack_size.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40767 b2dd03c8-39d4-4d8f-98ff-823fe69b080e
* 2013-05-16

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@40768 b2dd03c8-39d4-4d8f-98ff-823fe69b080e