timeout.rb: same object across fiber

* lib/timeout.rb (Timeout::ExitException.catch): do not freeze the
  exception for tag, so that the same object can be passed to the
  target fiber without duplication to attach backtrace at raise.

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@48467 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/timeout.rb

@@ -31,17 +31,16 @@ module Timeout
     def self.catch(*args)
       exc = new(*args)
       exc.instance_variable_set(:@thread, Thread.current)
-      exc.freeze
       ::Kernel.catch(exc) {yield exc}
     end
 
     def exception(*)
+      # TODO: use Fiber.current to see if self can be thrown
       if self.thread == Thread.current
         bt = caller
         begin
           throw(self, bt)
         rescue UncaughtThrowError
-          raise Error, message, backtrace
         end
       end
       self