RFR 9 : 8160370 : System.getProperty("os.version") returns "Unknown" on Mac

[Brent Christian]

Hi,

Please review the following change for JDK 9:

Bug:
https://bugs.openjdk.java.net/browse/JDK-8160370
Webrev:
http://cr.openjdk.java.net/~bchristi/8160370/webrev.00/

The fix for 7131356 fills in the "os.version" system property on Mac 
using [NSProcessInfo operatingSystemVersion], available starting in Mac 
OS 10.9.

While JDK 9 will not support versions of Mac OS prior to 10.9 [1], not 
all testing infrastructure has been updated, and we've seen failures of

java/lang/System/OsVersionTest.java

The code to restore behavior on older Mac systems is only a few lines, 
so that seems like a good way to get testing going again.

Thanks,
-Brent

1. https://jdk9.java.net/jdk9_supported_platforms.html
2. https://bugs.openjdk.java.net/browse/JDK-8156132