config-parser: Add section iterator API

The X backend needs to iterate through all outputs.
diff --git a/shared/config-parser.h b/shared/config-parser.h
index 949f4d6..794e09c 100644
--- a/shared/config-parser.h
+++ b/shared/config-parser.h
@@ -102,6 +102,11 @@
 void
 weston_config_destroy(struct weston_config *config);
 
+int weston_config_next_section(struct weston_config *config,
+			       struct weston_config_section **section,
+			       const char **name);
+
+
 #ifdef  __cplusplus
 }
 #endif