SERVER-15262: fsynclock thread after downgrade to global S should unlock flush lock as it doesn't need it
SERVER-15541 RecoveryUnit::commitAndRestart to avoid WriteUnitOfWork
SERVER-15541 SERVER-15652 implement timing-based yielding
SERVER-15713: do not buffer replicated ops once primary
SERVER-15060: remove failing large set test
SERVER-15733 Wait longer for a primary in jstests/replsets/replsetprio1.js.

With the 30 second lease time, it is possible for it to take just over 30 seconds to elect
a new primary in replsetprio1.js.  Bump the wait time in the test to 60 seconds.
SERVER-15541 add invariants to catch yielding within a WriteUnitOfWork
SERVER-15262 Yield the flush lock even if it is for the LocalDB
SERVER-15686 remove unneeded blacklist code and tests from RangeDeleter
SERVER-15750 Break deadlock cycle by not holding the global lock while acquiring the bgsync mutex.
SERVER-15747 stepdown for the lease time after failed election
SERVER-15711: DurThread is at front of queue, but times out
SERVER-15706 Refactor internal user authentication
SERVER-15761 Acquire collection-level lock for getting TTL indexes.

Also need to check that the CollectionCatalogEntry is non-NULL
since the specified namespace may not be found in the catalog.
SERVER-15762: index_retry.js - wait for journal flush
SERVER-15756 Make sure we don't let a new reconfig start while we're still processing a hb reconfig
SERVER-15733 reinstate yea delay of 30 seconds in the LegacyReplicationCoordinator
SERVER-15711: DurThread sleep when fifo lock takes over
Mega commit of kv_engine_impl and a kv_heap engine for testing. Needs a
full description of everything that changed and a jira ticket number.