Make CRYPTO_num_locks() return 1

malloc(0) might return NULL and code for the old callbacks might fail,
instead just say they should allocate 1 entry.
Reviewed-by: NMatt Caswell <matt@openssl.org>

GH: #1266

include/openssl/crypto.h

@@ -215,7 +215,7 @@ void *CRYPTO_get_ex_data(const CRYPTO_EX_DATA *ad, int idx);
  * On the other hand, the locking callbacks are no longer used.  Consequently,
  * the callback management functions can be safely replaced with no-op macros.
  */
-#  define CRYPTO_num_locks()            (0)
+#  define CRYPTO_num_locks()            (1)
 #  define CRYPTO_set_locking_callback(func)
 #  define CRYPTO_get_locking_callback()         (NULL)
 #  define CRYPTO_set_add_lock_callback(func)