support insert argument type json.RawMessage

[domyway]

if use type json.RawMessage for the args, return fmt.Errorf("invalid argument type %T", args[i]) .

i have write some test .

go-sql-driver/mysql@1.6.0 handle json.RawMessage inside :

for i, arg := range args {
			// build NULL-bitmap
			if arg == nil {
				nullMask[i/8] |= 1 << (uint(i) & 7)
				paramTypes[i+i] = byte(fieldTypeNULL)
				paramTypes[i+i+1] = 0x00
				continue
			}

			if v, ok := arg.(json.RawMessage); ok {
				arg = []byte(v)
			}
			// cache types and values
			switch v := arg.(type) {
			case int64:
                          blablablabla.....