RFR: 8199443: Nashorn multithread bottleneck with "use strict"

[Hannes Wallnöfer]

Please review:

Bug: https://bugs.openjdk.java.net/browse/JDK-8199443
Webrev: http://cr.openjdk.java.net/~hannesw/8199443/webrev/

If we make sure the property maps for strict functions and arguments are set up 
correctly (they weren’t before) we can skip setting the property in 
ScriptObject#initUserAccessors.

Thanks,
Hannes