RFR(xs): 8202325: [aix] disable warnings-as-errors by default

[Thomas Stüfe]

Hi all,

may I have reviews please:

https://bugs.openjdk.java.net/browse/JDK-8202325
http://cr.openjdk.java.net/~stuefe/webrevs/8202325-aix-disable-warnings-as-errors/webrev.00/webrev/

We decided to disable warnings as errors by default on AIX. This is a
pragmatic decision - we will never be able to fix all the many xlC
warnings and the build since long only worked when disabling
warnings-as-errors.

So, might as well make this the default.

Best regards, Thomas