Queries that select concatenated constant strings now have
colname and value that match. For example,
SELECT '123' 'x';
will return a result where the column name and value both
are '123x'.
Review: Daniel Black
This patch changes the main name of 3 byte character set from utf8 to
utf8mb3. New old_mode UTF8_IS_UTF8MB3 is added and set TRUE by default,
so that utf8 would mean utf8mb3. If not set, utf8 would mean utf8mb4.
Standard compatible behavior for UPDATE: all assignments in SET
are executed "simultaneously", not left-to-right. And `SET a=b,b=a`
will swap the values.
