MINOR: h1: add struct h1m for basic HTTP/1 messages

This one is much simpler than http_msg and will be used in the HTTP
parsers involved in the H2 to H1 gateway.
diff --git a/include/proto/h1.h b/include/proto/h1.h
index 8a0e265..6bd7537 100644
--- a/include/proto/h1.h
+++ b/include/proto/h1.h
@@ -267,5 +267,16 @@
 	return -buffer_count(buf, ptr, ptr_stop);
 }
 
+/* initializes an H1 message */
+static inline struct h1m *h1m_init(struct h1m *h1m)
+{
+	h1m->state = HTTP_MSG_RQBEFORE;
+	h1m->flags = 0;
+	h1m->curr_len = 0;
+	h1m->body_len = 0;
+	h1m->err_pos = 0;
+	h1m->err_state = 0;
+	return h1m;
+}
 
 #endif /* _PROTO_H1_H */