usql updates, lexer changes

ml_date.cpp

@@ -18,8 +18,8 @@ std::string date_to_string(const long datetime, const std::string format) {
 		std::string result = {mbstr};
 		return result;
 	}
-	// TODO exception here
-    return "invalid argument";
+
+	throw std::runtime_error("date_to_string invalid date string or format");
 }
 
 time_t time_to_epoch ( const struct tm *ltm, int utcdiff ) {
@@ -70,8 +70,7 @@ long string_to_date(const std::string &datestr, const std::string &format) {
 	    return time_to_epoch(timeinfo, -1 * timeinfo->tm_gmtoff);
 	}
 
-	// throw Exception("invalid date string or format");
-	return -1;
+	throw std::runtime_error("string_to_date invalid date string or format");
 }