Merge the wip/gapplication branch

This adds a GApplication object to GIO, which is the core of
an application support class, supporting
- uniqueness
- exporting actions (simple scripting)
- standard actions (quit, activate)

The implementation for Linux uses D-Bus, takes a name on the
session bus, and exports a org.gtk.Application interface.

Implementations for Win32 and OS X are still missing.

gio/gio.symbols

@@ -26,6 +26,27 @@ g_vfs_get_local
 #endif
 #endif
 
+#if IN_HEADER(__G_APPLICATION_H__)
+#if IN_FILE(__G_APPLICATION_C__)
+g_application_get_type G_GNUC_CONST
+g_application_new
+g_application_new_and_register
+g_application_get_instance
+g_application_get_id
+g_application_set_action_enabled
+g_application_get_action_enabled
+g_application_get_action_description
+g_application_add_action
+g_application_remove_action
+g_application_register_with_data
+g_application_invoke_action
+g_application_list_actions
+g_application_run
+g_application_quit
+g_application_is_remote
+#endif
+#endif
+
 #if IN_HEADER(__G_APP_INFO_H__)
 #if IN_FILE(__G_APP_INFO_C__)
 g_app_info_get_type G_GNUC_CONST