Fixes:

Bug #18942: DROP DATABASE does not drop an orphan FOREIGN KEY constraint
  Fix Bug#18942 by dropping all foreign key constraints at the end of
  DROP DATABASE. Usually, by then, there are no foreign constraints
  left because all of them are dropped when the relevant tables are
  dropped. This code is to ensure that any orphaned FKs are wiped too.

Bug #29157: UPDATE, changed rows incorrect
  Return HA_ERR_RECORD_IS_THE_SAME from ha_innobase::update_row() if no
  columns were updated.

Bug #32440: InnoDB free space info does not appear in SHOW TABLE STATUS or I_S
  Put information about the free space in a tablespace in
  INFORMATION_SCHEMA.TABLES.DATA_FREE. This information was previously
  available in INFORMATION_SCHEMA.TABLES.TABLE_COMMENT, but MySQL has
  removed it from there recently.
  The stored value is in kilobytes.
  This can be considered as a permanent workaround to
  http://bugs.mysql.com/32440. "Workaround" becasue that bug is about the
  data missing from TABLE_COMMENT and this is actually not solved.