fixes
MDEV-14732 mysql.db privileges evaluated on order of grants rather than hierarchically
MDEV-8269 Correct fix for Bug #20181776 :- ACCESS CONTROL DOESN'T MATCH MOST SPECIFIC HOST WHEN IT CONTAINS WILDCARD

reimplement the old ad hoc get_sort() function to use a wildcard
pattern ordering logic that works correctly in may be all practical cases.

get_sort() is renamed to catch merge errors at compilation time.
moved to a separate included file, because of a long comment.