SERVER-15535 revert freshness changes w.r.t. priority
SERVER-15535 update slavemap optimes on heartbeats
SERVER-15647: make Extent Manager thread-safe and enable MMAPv1 CLL
SERVER-15244 More aggressive auto-split when total chunks are small
SERVER-15506 batch_write_commands tests generate too much output
SERVER-14668: Use server parameter to enable CLL

This does not affect storage engines that support document level locking.
SERVER-15535 adjust resync command handling synchronization
SERVER-15535 fix server6733.js to connect to a new sync source
SERVER-15695 disable flawed test
SERVER-15535 add arbiter to make shutdown test work
SERVER-15535 Do not immediately stand for reelection after stepping down for a higher priority node.
SERVER-13635: pass whether an index is unique or not down through SortedDataInterface
SERVER-13635: better txn lines for replication sync
SERVER-15683: add command to introspect OperationContext and RecoveryUnit
SERVER-13635: make test handle oplogs of different engines
SERVER-13635: txn boundary for chunk migration getting disk locs
SERVER-13635: fix race in kv db catalog entry
SERVER-13635: add hook to RecoveryUnit for when we are take out of and put back into service
SERVER-14973 consolidate shard key parsing, cleanup shard key patterns
Merge remote-tracking branch 'upstream/master'