Merge remote-tracking branch 'quintela/migration-next-20120808' into staging

Merge remote-tracking branch 'quintela/migration-next-20120808' into staging

* quintela/migration-next-20120808:
  Restart optimization on stage3 update version
  Add XBZRLE statistics
  Add migration accounting for normal and duplicate pages
  Change total_time to total-time in MigrationStats
  Add migrate_set_cache_size command
  Add XBZRLE to ram_save_block and ram_save_live
  Add xbzrle_encode_buffer and xbzrle_decode_buffer functions
  Add uleb encoding/decoding functions
  Add cache handling functions
  Add XBZRLE documentation
  Add migrate-set-capabilities
  Add migration capabilities