types: Fix integer_type_impl::parse_int() for bytes
types: Fix integer_type_impl::parse_int() for bytes

The integer_type_impl::parse_int() function uses boost::lexical_cast()
under the hood, which parses 8-bit numbers as characters. Fix the
function to lexical cast to 64-bit integer and convert the result to
integer_type_impl template type.

duarten/scylla,raphaelsc/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,raphaelsc/scylla,raphaelsc/scylla,scylladb/scylla