Clone to keep extended Logger methods for tagged logger

`#dup` resets the extended Logger methods that could come from enabling broadcasting. That would mean if we create a tagged logger from a Logger with broadcasting enabled (usually to stdout), the new tagged logger will not perform broadcasting.

activesupport/lib/active_support/tagged_logging.rb

@@ -79,7 +79,7 @@ module ActiveSupport
     end
 
     def self.new(logger)
-      logger = logger.dup
+      logger = logger.clone
 
       if logger.formatter
         logger.formatter = logger.formatter.dup

activesupport/test/tagged_logging_test.rb

@@ -214,4 +214,16 @@ class TaggedLoggingWithoutBlockTest < ActiveSupport::TestCase
 
     assert_equal "[BCX] [Jason] Funky time\n[BCX] Junky time!\n", @output.string
   end
+
+  test "keeps broadcasting functionality" do
+    broadcast_output = StringIO.new
+    broadcast_logger = ActiveSupport::TaggedLogging.new(Logger.new(broadcast_output))
+    @logger.extend(ActiveSupport::Logger.broadcast(broadcast_logger))
+
+    tagged_logger = @logger.tagged("OMG")
+    tagged_logger.info "Broadcasting..."
+
+    assert_equal "[OMG] Broadcasting...\n", @output.string
+    assert_equal "[OMG] Broadcasting...\n", broadcast_output.string
+  end
 end