Prefer block_given? to iterator?

git-svn-id: svn+ssh://ci.ruby-lang.org/ruby/trunk@66866 b2dd03c8-39d4-4d8f-98ff-823fe69b080e

lib/irb/cmd/fork.rb

@@ -21,7 +21,7 @@ module IRB
           class << self
             alias_method :exit, ExtendCommand.irb_original_method_name('exit')
           end
-          if iterator?
+          if block_given?
             begin
               yield
             ensure