Fix comment typos reported on the mailing list.  No changes to code.
Clarification of the meaning of the second parameter to the busy-handler
callback.  No changes to code.
If a table is the right operand of a LEFT JOIN, then any column of that
table can be NULL even if that column as a NOT NULL constraint.
Fix for ticket [6f2222d550f5b0ee7ed].
Performance enhancement for single-table queries with many OR-connected
WHERE clause terms and multiple indexes with the same left-most columns.
Make sure that a DISTINCT query with an ORDER BY works correctly even if
it uses a descending index.  Fix for ticket [c5ea805691bfc4204b1cb9e].
Fix the autoconf and MSVC makefiles, which have been broken for nearly a
month.  :-(
Fix compiler warnings.