[cogl] onscreen: add missing transfer annotation

[Robert Bragg <rbragg src gnome org>]

commit 7047106c9d54af008ab962669e9922aa89a6cd1f
Author: Lionel Landwerlin <llandwerlin gmail com>
Date:   Tue Sep 3 16:17:55 2013 +0100

    onscreen: add missing transfer annotation
    
    Reviewed-by: Robert Bragg <robert linux intel com>
    
    (cherry picked from commit 777be3895da8c2e5ce71135c3c1bf5707f2821d9)

 cogl/cogl-onscreen.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/cogl/cogl-onscreen.h b/cogl/cogl-onscreen.h
index d9582fa..a28559c 100644
--- a/cogl/cogl-onscreen.h
+++ b/cogl/cogl-onscreen.h
@@ -52,7 +52,7 @@ typedef struct _CoglOnscreen CoglOnscreen;
  * configured before later being allocated, either implicitly when
  * it is first used or explicitly via cogl_framebuffer_allocate().
  *
- * Return value: A newly instantiated #CoglOnscreen framebuffer
+ * Return value: (transfer full): A newly instantiated #CoglOnscreen framebuffer
  * Since: 1.8
  * Stability: unstable
  */