image.cpp: remove unused macros, in-place conversion from rgba to argb.

main.cpp: change move assignment in generic raii wrapper, change the Interpreter from struct to class to better reflect what it actually is.
window.cpp: implement a workaround for the window to not freeze during dragging. fuck you ms.

include/image.h

@@ -10,9 +10,9 @@ extern "C" {
 #include <stdint.h>
 #endif
 
-// Loads an image file as ARGB8888. Returns pointer to pixel data, sets width/height.
+// Loads an image file as ARGB8888. Returns pointer to pixel data, sets width/height. NULL on failure.
 uint32_t* image_load(const char* filename, int* width, int* height);
-// Loads and resizes an image file to desired dimensions as ARGB8888. Returns pointer to pixel data.
+// Loads and resizes an image file to desired dimensions as ARGB8888. Returns pointer to pixel data. NULL on failure.
 uint32_t* image_load_resized(const char* filename, int desired_width, int desired_height);
 // Frees image data.
 void image_free(uint32_t* data);