RFR: Consistent liveness for humongous regions

[Roman Kennke]

When counting liveness on humongous regions, we current give all
liveness to the start region, and leave the rest alone. For this
reason, we have put exceptions to several asserts. This patch makes
liveness counting more consistent for humongous regions by spreading
it over all involved regions, just as it is done at allocation time.
It also removes the exceptions in the asserts. It also removes an
exception for traversal-gc, which I believe is fixed by this mornings
liveness init patch.

Passes hotspot_gc_shenandoah

http://cr.openjdk.java.net/~rkennke/fix-humongous-live/webrev.00/

Ok?

Roman