RFR 8194929 : Unreferenced FileDescriptors not closed

[Roger Riggs]

Please review a fix for a missing entry in the mapfiles.  The missing 
entry point
caused the closing of unreferenced FileDescriptors to be skipped.

The tests for FileInputStream, FileOutputStream, and RandomAccess file 
unreferenced
FileDescriptors have been updated to verify the raw fds have been closed.

This fix applies to JDK 10+.

Webrev:
http://cr.openjdk.java.net/~rriggs/webrev-fd-cleanup-8194929/index.html

Issue:
   https://bugs.openjdk.java.net/browse/JDK-8194929

Thanks, Roger