Given the value in a statement like "SET SQL_MODE=..." this parser
is capable of deducing whether SQL_MODE is set to DEFAULT or ORACLE
or something else.
SetParser is capable of returning the exact variable and value
of a "SET X=Y" statement, in the cases where X is of a specific
set of variables; currently "SQL_MODE" and "@MAXSCALE...".
The actual value of the SET statement also needs to be parsed in
the case of SQL_MODE, but it becomes unnecessary convoluted if that
information somehow should conditionally be expressable in a return
value.
So, the value will be parsed separately.
