RFR: 8199869: Missing copyright headers in nashorn source code

[Hannes Wallnöfer]

Please review (trivial change, two copyright headers added):

Bug: https://bugs.openjdk.java.net/browse/JDK-8199869
Webrev: http://cr.openjdk.java.net/~hannesw/8199869/webrev/

Thanks,
Hannes