Mark some variables more consistently as SRD_PRIV.
diff --git a/instance.c b/instance.c
index 5f48b71..8a5ddef 100644
--- a/instance.c
+++ b/instance.c
@@ -28,7 +28,7 @@
 
 /** @cond PRIVATE */
 
-extern GSList *sessions;
+extern SRD_PRIV GSList *sessions;
 
 /* type_logic.c */
 extern SRD_PRIV PyTypeObject srd_logic_type;