Add 'raw' mode to benchmark
Add 'raw' mode to benchmark

'Raw' mode will scan the string for a single character via a loop. Can
be used as a baseline for comparing to JSON parsing overhead vs actual
string scanning.

mnunberg/jsonsl,snej/jsonsl,mnunberg/jsonsl,snej/jsonsl,snej/jsonsl,mnunberg/jsonsl,mnunberg/jsonsl,snej/jsonsl