RFR (XXS) 8229835: Shenandoah should recommend -Xlog:safepoint+stats=info

[Florian Weimer]

Shenandoah refers to a Hotspot option that was removed in OpenJDK 12.

Bug: <https://bugs.openjdk.java.net/browse/JDK-8229835>
Webrev: <http://cr.openjdk.java.net/~fweimer/8229835/webrev.00/>

(Note: The replacement option is different OpenJDK 12.)

Thanks,
Florian