few tool functions for the plugin implementation

* plugin_name() to figure out the name of the plugin
 * plugin_refinc() and plugin_refdec() to manage the refcount

src/backend/plugin.c

@@ -154,7 +154,8 @@ lumiera_plugin_error (LumieraPlugin self)
   return self->error;
 }
 
-void *
+
+void*
 lumiera_plugin_handle (LumieraPlugin self)
 {
   REQUIRE (self);
@@ -162,6 +163,27 @@ lumiera_plugin_handle (LumieraPlugin self)
 }
 
 
+const char*
+lumiera_plugin_name (LumieraPlugin self)
+{
+  return self?self->name:NULL;
+}
+
+
+void
+lumiera_plugin_refinc (LumieraPlugin self)
+{
+  ++self->refcnt;
+}
+
+
+void
+lumiera_plugin_refdec (LumieraPlugin self)
+{
+  --self->refcnt;
+}
+
+
 int
 lumiera_plugin_discover (LumieraPlugin (*callback_load)(const char* plugin),
                          int (*callback_register) (LumieraPlugin))
@@ -370,7 +392,6 @@ lumiera_plugin_delete_fn (PSplaynode node)
 
   ENSURE (!self->refcnt, "plugin %s still in use at shutdown", self->name);
 
-
   const char* ext = strrchr (self->name, '.');
 
   LumieraPlugintype itr = lumiera_plugin_types;

src/backend/plugin.h

@@ -137,6 +137,34 @@ void*
 lumiera_plugin_handle (LumieraPlugin self);
 
 
+/**
+ * Query the plugin name
+ * The name is the path and filname under which it was loaded
+ * @param self plugin to query
+ * @return pointer to the name string
+ */
+const char*
+lumiera_plugin_name (LumieraPlugin self);
+
+
+/**
+ * Increment refcount
+ * @internal
+ * @param self plugin which refcount to increment
+ */
+void
+lumiera_plugin_refinc (LumieraPlugin self);
+
+
+/**
+ * Decrement refcount
+ * @internal
+ * @param self plugin which refcount to decrement
+ */
+void
+lumiera_plugin_refdec (LumieraPlugin self);
+
+
 /**
  * Tries to unload a plugin.
  * When the Plugin is unused, then all resources associated with it are freed and it will be removed from memory