Merge pull request #4506 from FedericoCeratto/patch-12

Add copyright header

lib/pure/punycode.nim

@@ -1,3 +1,11 @@
+#
+#
+#            Nim's Runtime Library
+#        (c) Copyright 2016 Andreas Rumpf
+#
+#    See the file "copying.txt", included in this
+#    distribution, for details about the copyright.
+#
 
 import strutils
 import unicode