Include stdlib.h and changed function declaration to extern

src/includes/kernel/util.h

@@ -13,6 +13,7 @@ arm-016-util.h
 #define COLOUR_DELTA    0.05    /* Float from 0 to 1 incremented by this amount */
 
 #include <math.h>
+#include <stdlib.h>
 
 typedef struct {
     float r;
@@ -24,8 +25,8 @@ typedef struct {
 
 extern void setColor(volatile unsigned char* fb, colour_t pixel, long x, long y, long pitch);
 
-int * getCoordinates();
-double scale_to_x_origin(int);
-int scale_to_y_pixel(double);
+extern int * getCoordinates();
+extern double scale_to_x_origin(int);
+extern int scale_to_y_pixel(double);
 
 #endif