Use struct for vec3_t instead of array

gpu.h

@@ -6,9 +6,12 @@
 
 #define SWAPCHAIN_IMG_BUFFER_SIZE 4
 
-typedef float vec3_t[3];
 typedef float mat4_t[16];
 
+typedef struct {
+	float x, y, z;
+} vec3_t;
+
 typedef struct {
 	vec3_t position;
 	vec3_t colour;