Factor out function to get value with broadest digits

src/strings.cpp

@@ -116,14 +116,7 @@ void SetDParamMaxValue(uint n, uint64 max_value, uint min_count, FontSize size)
  */
 void SetDParamMaxDigits(uint n, uint count, FontSize size)
 {
-	uint front = 0;
-	uint next = 0;
-	GetBroadestDigit(&front, &next, size);
-	uint64 val = count > 1 ? front : next;
-	for (; count > 1; count--) {
-		val = 10 * val + next;
-	}
-	SetDParam(n, val);
+	SetDParam(n, GetBroadestDigitsValue(count, size));
 }
 
 /**