RFR: 8030350 : (s) Enable additional compiler warnings for GCC

[Mike Duigou]

Hello all;

I have added the BSD supported requested in previous reviews and I believe this change is ready to go in.

http://cr.openjdk.java.net/~mduigou/JDK-8030350/2/webrev/

I need a sponsor for the hotspot repo portion of the change.

I've also generated build log diffs to illuminate the additional warnings produced and will file bugs shortly for a few of the cases.

Mike