Merge remote-tracking branch 'quintela/migration-anthony-v2' into staging

Merge remote-tracking branch 'quintela/migration-anthony-v2' into staging

* quintela/migration-anthony-v2:
  Maintain the number of dirty pages
  dirty bitmap: abstract its use
  Exit loop if we have been there too long
  Only calculate expected_time for stage 2
  Only TCG needs TLB handling
  No need to iterate if we already are over the limit
  Add tracepoints for savevm section start/end
  Add spent time for migration
  Add migration_end function
  Add debugging infrastructure
  Add save_block_hdr function
  Add MigrationParams structure
  Add missing check for host_from_stream_offset return value for RAM_SAVE_FLAG_PAGE