change math for use std::round() intead of rounding variable

else, final value ever truncated, and don't round damage before bonus calculation(leadership and Tod) make a UI bug(damage colored like if leadership used same if not)

src/utils/math.hpp

@@ -79,8 +79,7 @@ constexpr T modulo(T num, int mod, T min = 0)
  */
 constexpr int round_damage(double base_damage, int bonus, int divisor) {
 	if (base_damage==0) return 0;
-	const int rounding = divisor / 2 - (bonus < divisor || divisor==1 ? 0 : 1);
-	return std::max<int>(1, static_cast<int>((base_damage * bonus + rounding) / divisor));
+	return std::max<int>(1, std::round((base_damage * bonus) / divisor));
 }
 
 template<typename Cmp>