ERR_LIB_USER should be the last error.

Consumers sometimes use ERR_LIB_USER + <favorite number> instead of
ERR_get_next_error_library. To avoid causing them grief, keep ERR_LIB_USER
last.

Change-Id: Id19ae7836c41d5b156044bd20d417daf643bdda2
Reviewed-on: https://boringssl-review.googlesource.com/5290
Reviewed-by: Adam Langley <agl@google.com>
diff --git a/include/openssl/err.h b/include/openssl/err.h
index bf1cf47..0a90b0e 100644
--- a/include/openssl/err.h
+++ b/include/openssl/err.h
@@ -430,8 +430,8 @@
   ERR_LIB_HMAC,
   ERR_LIB_DIGEST,
   ERR_LIB_CIPHER,
-  ERR_LIB_USER,
   ERR_LIB_HKDF,
+  ERR_LIB_USER,
   ERR_NUM_LIBS
 };