RFR: 8180466: Clock.systemUTC has low resolution on Windows

[David Holmes]

bug: https://bugs.openjdk.java.net/browse/JDK-8180466
webrev: http://cr.openjdk.java.net/~dholmes/8180466/webrev/

There is a new higher-resolution system time call available in Windows 
8+ and Windows Server 2012+. This enhancement uses the API if it is 
available at runtime.

Testing:
  - manual testing using the little "benchmark" in the bug report on 
Windows 7 (no new API) and later
  - java.time tests

Thanks,
David