[vala/0.40] libvaladoc: Fix a couple of C compiler warnings

[Rico Tzschichholz <ricotz src gnome org>]

commit 5758e19695d5cd62851997dd0edac9f1b9dda4bc
Author: Rico Tzschichholz <ricotz ubuntu com>
Date:   Mon Sep 28 12:44:12 2020 +0200

    libvaladoc: Fix a couple of C compiler warnings

 libvaladoc/gvc-compat.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)
---
diff --git a/libvaladoc/gvc-compat.c b/libvaladoc/gvc-compat.c
index 9ec37e616..962f74965 100644
--- a/libvaladoc/gvc-compat.c
+++ b/libvaladoc/gvc-compat.c
@@ -25,7 +25,16 @@
 /* Compat-layer for Graphviz with/without cgraph support */
 
 void
-valadoc_compat_gvc_init ()
+valadoc_compat_gvc_init (void);
+
+Agnode_t*
+valadoc_compat_gvc_graph_create_node (Agraph_t* graph, const char *name);
+
+Agraph_t*
+valadoc_compat_gvc_graph_new (const char *name);
+
+void
+valadoc_compat_gvc_init (void)
 {
 #ifndef WITH_CGRAPH
        aginit ();