Release Note: G1 now collects unreachable Humongous objects during young collections

G1 now tries to collect humongous objects of primitive type (char, integer, long, double) with few or no references from other objects at any young collection. During young collection, G1 checks if any remaining incoming references to these humongous objects are current. G1 will reclaim any humongous object having no remaining incoming references.

Three new experimental JVM options to control this behavior that have been added with this change:

1. G1EagerReclaimHumongousObjects - This option controls whether G1 makes any attempt to reclaim unreachable humongous objects at every young GC. Default is enabled.
2. G1EagerReclaimHumongousObjectsWithStaleRefs - When this option is enabled G1 attempts to reclaim humongous objects that may have a few stale incoming references at every young GC. Default is enabled.
3. G1TraceEagerReclaimHumongousObjects - This option enables printing of some information about the collection of humongous objects at every young GC. Default is disabled.