Some platforms do not implement `msize()` or similar functions. It would be nice if one could override the "common" memory methods, and leave `xSize` a `NULL` pointer:
```
struct sqlite3_mem_methods m = {0};
m.xMalloc = my_malloc;
m.xFree = my_free;
m.xRealloc = my_realloc;
sqlite3_config(SQLITE_CONFIG_MALLOC, &m); // error handling intentionally left out
```