purge riff-raff
purge DBIx::Interp
purge strict mode
purge STDERR-only tracing feature
use done_testing
remove vestige
remove confused code

The main interp function never returns the bind values (they are passed
back through a state variable). It is therefore nonsensical to ever look
for them among the things it returns and any code that is conditional on
it ever returning them is dead code.
handle simple cases first
inline _sql_interp_list
basic sanity pass
simplify INSERT case
simplify IN case
simplify SET case
simply FROM case
switch to queue
fix wrong use of non-local state
remove kludge state
use queue to handle sql() w/o recursion
remove duplicate code from FROM case
simplify parse_resultset