Add comments about why the InnoDB latching order is obeyed also for the MySQL query cache mutex; add an error printf if that is not the case
sync0sync.h:
  Assign sync0sync.h ranks also for the MySQL query cache mutex and the MySQL binlog mutex; the latching order must be obeyed also for these
row0ins.c:
  Add a comment why the query cache invalidate operation cannot deadlock in a cascaded FOREIGN KEY operation