RFR(M) JDK-8031819: Remove legacy jdk checks and code

[harold seigel]

Hi,

Please review this JDK 9 fix for bug JDK-8031819.  The fix removes 
legacy code for old JDK versions.  Although the webrev contains lots of 
files, the changes are not complicated.

Open webrev: http://cr.openjdk.java.net/~hseigel/bug_8031819/
Bug: https://bugs.openjdk.java.net/browse/JDK-8031819

The fix was tested with the Hotspot JTREG tests, JCK Lang, VM, and 
API/java_lang tests, nsk Quick tests, and JPRT.

Thanks! Harold