Summary: Catch OutOfMemoryError in reference handler thread if caused by allocation of an InterruptedException
Reviewed-by: dholmes, alanb

Reviewed-by: chegar, ksrini

4268317: (ref) Reference.isEnqueued() can return true when instance not enqueued
Summary: The reference handler now declares, and assumes, that the discovered field, rather than the next field, is (to be) used to link the entries in the pending list, thus allowing a reference object to be safely enqueued even while it is in the pending state. Also added slightly modified regression tests from the two bug reports.
Reviewed-by: mchung, alanb, jcoomes

Reviewed-by: darcy, weijun