RFR [8042470]: (fs) Path.register doesn't throw IllegalArgumentException if multiple OVERFLOW events are specified

[Alan Bateman]

I see Ivan has pushed this one already. I've created JDK-8042816 to fix 
up the PollingWatchService as otherwise the updated tests will fail on 
those platforms where we don't have a native implementation. The 
addition to Ivan's change is here:

http://cr.openjdk.java.net/~alanb/8042816/webrev/

Thanks,
Alan.