Replace all free calls with VVV_free[func]

This replaces all calls to SDL_free with a new macro, VVV_free, that
nulls the pointer afterwards. This mitigates any use-after-frees and
also completely eliminates double-frees. The same is done for any
function to free specific objects such as SDL_FreeSurface, with the
VVV_freefunc macro.

No exceptions for any of these calls, even if the pointer is discarded
or zeroed afterwards anyway. Better safe than sorry.

This is a macro rather than a function that takes in a
pointer-to-pointer because such a function would have type issues that
require casting and that's just not safe.

Even though SDL_free and other SDL functions already check for NULL, the
macro has a NULL check for other functions that don't. For example,
FAudioVoice_DestroyVoice does not check for NULL.

FILESYSTEM_freeMemory has been axed in favor of VVV_free because it
functionally does the same thing except for `unsigned char*` only.

desktop_version/src/ThirdPartyDeps.c

@@ -1,5 +1,7 @@
 #include <SDL_stdinc.h>
 
+#include "Alloc.h"
+
 /* Handle third-party dependencies' needs here */
 
 void* lodepng_malloc(size_t size)
@@ -14,5 +16,5 @@ void* lodepng_realloc(void* ptr, size_t new_size)
 
 void lodepng_free(void* ptr)
 {
-    SDL_free(ptr);
+    VVV_free(ptr);
 }