* Add a safe unserialize() wrapper for HistoryBlob classes
* Add a safe unserialize() wrapper for plain array data as used for
compressed internal storage by ConcatenatedGzipHistoryBlob and
DiffHistoryBlob.
* Fix tests broken by this.
* Fix unnecessary call to uncompress(), __wakeup() does this already.
Was a phan error now that we have more information about the type of
$obj.
* Add tests for successful unserialize and wakeup of WMF production
data.
Change-Id: Ic995dda16d9c6045b33f2fdae7f6575ac8329976
