Merge branch 'unstable'

* unstable: (140 commits)
  [box] add unique property to memcached index
  [core] repair statistics
  [core] remove limit of 4MB packet size between parent and child
  [core] mention about GNU make requirement
  [core, box] write cookie in span too
  [box] fix snap printing
  [core] fix memory leak when saving snapshot
  [core] partially rollback 8cb4a2b4, make incremental builds work again
  [core] repair reading of v04 snaps
  [core] update confetti: added property 'required'
  [core] flush stdio buffers when writing wal
  [feeder] support for tagged rows
  [core] remove cfg.h file hack, tweak scripts/indent
  [core] fix bug: cookie is 64 bit
  [core] default tags are negative
  [core, box] row dispatch based on tag
  [box] [client] [perl] hash_by
  [core, box] wal_write and snapshot_write row now explicitly require tag and cookie
  [core, box] support for cookie in WAL
  [core] refactor read_u{8,16,32,4}
  ...