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/Alloc.h

@@ -0,0 +1,19 @@
+#ifndef ALLOCGAME_H
+#define ALLOCGAME_H
+
+/* TODO: VVV_malloc, VVV_realloc, etc. */
+
+#define VVV_freefunc(func, obj) \
+    do \
+    { \
+        if (obj != NULL) \
+        { \
+            func(obj); \
+            obj = NULL; \
+        } \
+    } \
+    while (0)
+
+#define VVV_free(obj) VVV_freefunc(SDL_free, obj)
+
+#endif /* ALLOCGAME_H */