Native Milli code no longer necessary on JDK10 or greater

[cunei]

We can probably modify the Milli code to always use the standard Java calls if the property "java.version" says we are running on JDK10 or greater. The original pull request #92, submitted on 2017-12-06, referred to a then-pending JDK issue whose fix was eventually included in JDK10. We can avoid the JNA dispatching overhead if running on a JDK with a fully working get/setLastModifiedTime() call.

[eed3si9n]

Looks like this was fixed in #274