make vec4 and matrix types internal

include/twn_types.h

@@ -22,16 +22,6 @@ typedef struct Vec3 {
 } Vec3;
 
 
-/* a point in some three dimension space (floating point) */
-/* y goes up, x goes to the right */
-typedef struct Vec4 {
-    float x;
-    float y;
-    float z;
-    float w;
-} Vec4;
-
-
 /* 32-bit color data */
 typedef struct Color {
     uint8_t r;
@@ -49,10 +39,5 @@ typedef struct Rect {
     float h;
 } Rect;
 
-/* TODO: remove from here? */
-typedef struct Matrix4 {
-    Vec4 row[4];
-} Matrix4;
-
 
 #endif