Emit a better error message when the id in the key header is too long.

src/vfp.c

@@ -792,8 +792,8 @@ vfp_encrypt_init(struct vfp_ctx *ctx, struct vfp_entry *ent)
 				 DEFAULT_KEY_HDR + 1));
 	keyid_len = strlen(keyid);
 	if (keyid_len > MAX_ID_LEN)
-		return (VERR_ENC(ctx, "key id %s too long (%zd > 255)", keyid,
-				 keyid_len));
+		return (VERR_ENC(ctx, "key id \"%.80s...\" too long "
+				 "(length %zd > 255)", keyid, keyid_len));
 
 	if (common_alloc(ctx, &ece, 1) == VFP_ERROR)
 		return (VFP_ERROR);