- Don't assume that int and size_t have the same representation

  (and that malloc can be called with an int argument).
- Use proper prototypes (with argument list) for various function pointers,
  avoid casts  (however there are still many such cases left in these files).
- Avoid collissions in app_info_cmp if sizeof int != sizeof long.
- Use CRYPTO_LOCK_MALLOC in mem_dbg.c.