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/VFormat.h

@@ -5,7 +5,7 @@
  *  - vformat_cb       Calls a user-supplied callback function for each part of
  *                      the resulting string.
  *  - vformat_buf      Fills a user-supplied buffer with the result.
- *  - vformat_alloc    Allocates a buffer with the result (caller must SDL_free).
+ *  - vformat_alloc    Allocates a buffer with the result (caller must VVV_free).
  *
  * All include the following parameters:
  *  - format_string     The string which needs placeholders to be filled in