Add ASYNC error codes

Add ASYNCerr support to give some meaningful error message in the event of
a failure.

Reviewed-by: Rich Salz <rsalz@openssl.org>
diff --git a/crypto/err/err.c b/crypto/err/err.c
index 077929c..b7ca3de 100644
--- a/crypto/err/err.c
+++ b/crypto/err/err.c
@@ -157,6 +157,7 @@
     {ERR_PACK(ERR_LIB_FIPS, 0, 0), "FIPS routines"},
     {ERR_PACK(ERR_LIB_CMS, 0, 0), "CMS routines"},
     {ERR_PACK(ERR_LIB_HMAC, 0, 0), "HMAC routines"},
+    {ERR_PACK(ERR_LIB_ASYNC, 0, 0), "ASYNC routines"},
     {0, NULL},
 };