gir: keybindings: adhere to user_data naming convention

This helps g-ir-scanner recognizing the data parameter as context storage,
allowing object methods to be used as callback (via wrappers). It goes even
so far that g_object_unref is propery passed as destroy func to
keybindings_set_item_full() and plugin_set_key_group_full().

src/keybindings.h

@@ -55,7 +55,7 @@ typedef gboolean (*GeanyKeyGroupCallback) (guint key_id);
  * with the same key combination to handle it).
  *
  * @since 1.26 (API 226) */
-typedef gboolean (*GeanyKeyGroupFunc)(GeanyKeyGroup *group, guint key_id, gpointer pdata);
+typedef gboolean (*GeanyKeyGroupFunc)(GeanyKeyGroup *group, guint key_id, gpointer user_data);
 
 /** Function pointer type used for keybinding callbacks. */
 typedef void (*GeanyKeyCallback) (guint key_id);
@@ -67,7 +67,7 @@ typedef void (*GeanyKeyCallback) (guint key_id);
  * with the same key combination to handle it).
  *
  * @since 1.26 (API 226) */
-typedef gboolean (*GeanyKeyBindingFunc)(GeanyKeyBinding *key, guint key_id, gpointer pdata);
+typedef gboolean (*GeanyKeyBindingFunc)(GeanyKeyBinding *key, guint key_id, gpointer user_data);
 
 /** Represents a single keybinding action.
  *