Code review comment for lp:~hrvojem/percona-xtrabackup/rn-2.1.8-2.1

Suggested description of fixed bugs:

 Due to incorrect usage of ``posix_fadvise()`` hints, |Percona
 XtraBackup| discarded read-ahead buffers which resulted in higher
 ``I/O`` rate on the backup stage. Bug fixed :bug:`1093385`.

 Spurious trailing data blocks that would normally be ignored by InnoDB
 could lead to an assertion failure on the backup stage. Bug fixed
 :bug:`1177201`.

 A spurious warning message could cause issues with third-party wrapper
 scripts. Bug fixed :bug:`1271956`.

 :ref:`xbcrypt <xbcrypt>` could fail with the
 ``xbcrypt:xb_crypt_read_chunk: unable to read chunk iv size at offset``
 error under some circumstances. Bug fixed :bug:`1273196`.

 :ref:`xbstream <xbstream_binary>` could sometimes hang when extracting
 a broken or incomplete input stream. Bug fixed :bug:`1273207`.

 Preparing backups of MySQL or Percona Server 5.6 could raise an
 assertion failure in |Percona XtraBackup|. Bug fixed :bug:`1273468`.

 The downtime is decreased when the --safe-slave-backup option is used
 to backup a replication slave. The SQL thread is now
 started before a temporary copy of redo log is streamed into the final
 location. Bug fixed :bug:`1284778`.

 Disabled the "binary version check" functionality in the VersionCheck
 module due to security concerns. Bug fixed :bug:`1285166`.

 Other bugs fixed: :bug:`1284078`.