update string_view lite to version 1.6.0 (#1677)
update string_view lite to version 1.6.0 (#1677)

This is the header as seen in the current master branch,
commit d27d7b5081406a35b41cb16b321be8833b4cd811, on
<https://github.com/martinmoene/string-view-lite>.
lemire/simdjson,lemire/simdjson,lemire/simdjson,lemire/simdjson,lemire/simdjson,lemire/simdjson