Fix for loop for C99

> ui/helpers.c:78:2: error: ‘for’ loop initial declarations are only allowed in C99 mode

ui/helpers.c

@@ -75,7 +75,8 @@ char * hex_to_bitmap(char hex_digit) {
 
 	char *bitmap = malloc(5 * sizeof(char));
 	bitmap[4] = '\0';
-	for(int i = 3; i >= 0; i--) {
+	int i;
+	for(i = 3; i >= 0; i--) {
 		bitmap[i] = digit % 2 ? '1' : '0';
 		digit /= 2;
 	}