[8u] RFR: 8019470: Changes needed to compile JDK 8 on MacOS with clang compiler

[Simon Tooke]

Hello, I would like to backport this patch to 8u to partially enable building 8u with clang.  
This is an Oracle JDK 8u feature parity patch.

The patch applies with minimal changes (line numbers, etc). 
I wasn’t sure if it needed to be put out for review, but thought to err on the side of caution.

This patch is not all that is required to enable compiling on macOS with a recent Xcode, but it is a step forward.

Thank you for your time,
-Simon

JBS: https://bugs.openjdk.java.net/browse/JDK-8019470 <https://bugs.openjdk.java.net/browse/JDK-8019470>

Original patch: http://hg.openjdk.java.net/jdk9/jdk9/rev/77c150b417d8 <http://hg.openjdk.java.net/jdk9/jdk9/rev/77c150b417d8> 

Modified webrev: http://cr.openjdk.java.net/~stooke/webrevs/jdk-8019470-jdk8u/00/00/ <http://cr.openjdk.java.net/~stooke/webrevs/jdk-8019470-jdk8u/00/00/>