Ensure Async is deinited properly

The global thread local keys were not being deinited properly in async.

Reviewed-by: Rich Salz <rsalz@openssl.org>

crypto/async/async.c

@@ -351,8 +351,6 @@ int async_init(void)
     return 1;
 }
 
-/* TODO: FIXME: This needs to be called by something!!! */
-void async_deinit(void);
 void async_deinit(void)
 {
     CRYPTO_THREAD_cleanup_local(&ctxkey);