ZapUnusedHeapArea

[Tom Rodriguez]

Is there any interest in adding product support for ZapUnusedHeapArea?  I implemented it while debugging what turned out to be a card marking issue in the compiler but I figured I'd ask before blowing it away.  The webrev is at http://cr.openjdk.java.net/~never/zapunused.  It's a moderately useful flag when debugging stale oop issues with the compiler since it causes you to die pretty much at the first use of the stale pointer.

tom