Merge branch 'xlog_ng' into unstable

* xlog_ng:
  [core] indent
  [core] feeder stream versioning, refactored remote recovery
  [core] fix wording
  [core, feeder] support for v11 rows over network replication
  [core] fix feeder build
  [core] stop statistic aging if no data sources present
  [box] implicit row tags
  [core, box] implement support for v11 snap
  [core] repair magick lookup
  [core, box] factor out conversion to v11 row format
  [core] panic if recovery failed
  [core, box] unified xlog & snap io, unified robust ondisk format
  [core] add read_u16
  [core] remove dead code