Merge tag 'upstream/5.5.57' into ubuntu-14.04

Upstream version 5.5.57

# gpg: Signature made su 23. heinäkuuta 2017 23.35.34 EEST
# gpg:                using RSA key BED8449FCEE8DA88
# gpg: Good signature from "Otto Kekäläinen <otto@seravo.fi>" [full]
# gpg:                 aka "Otto Kekäläinen <otto@kekalainen.net>" [full]
# gpg:                 aka "Otto Kekäläinen <otto@fsfe.org>" [full]
# gpg:                 aka "Otto Kekäläinen <otto@linux.com>" [full]
# gpg:                 aka "Otto Kekäläinen <otto.kekalainen@seravo.fi>" [full]
# gpg:                 aka "Otto Kekäläinen <otto@mariadb.org>" [undefined]
# gpg:                 aka "Otto Kekäläinen <otto@debian.org>" [undefined]
# gpg:                 aka "Otto Kekäläinen <otto@sange.fi>" [full]