[gdk-pixbuf] Fix introspection data for gdk_pixbuf_new, gdk_pixbuf_copy and gdk_pixbuf_composite_color_simple

[Emmanuele Bassi <ebassi src gnome org>]

commit 3e8502a8cbe23d2db84bd91d4f775e57522bfdbe
Author: Iñaki García Etxebarria <garetxe gmail com>
Date:   Sun Nov 5 15:46:59 2017 +0100

    Fix introspection data for gdk_pixbuf_new, gdk_pixbuf_copy and gdk_pixbuf_composite_color_simple
    
    https://bugzilla.gnome.org/show_bug.cgi?id=789935

 gdk-pixbuf/gdk-pixbuf-scale.c |    2 +-
 gdk-pixbuf/gdk-pixbuf.c       |    4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)
---
diff --git a/gdk-pixbuf/gdk-pixbuf-scale.c b/gdk-pixbuf/gdk-pixbuf-scale.c
index e9514ef..e9c244e 100644
--- a/gdk-pixbuf/gdk-pixbuf-scale.c
+++ b/gdk-pixbuf/gdk-pixbuf-scale.c
@@ -382,7 +382,7 @@ gdk_pixbuf_scale_simple (const GdkPixbuf *src,
  * @dest_height and alpha blending the result with a checkboard of colors
  * @color1 and @color2.
  * 
- * Return value: (transfer full): the new #GdkPixbuf, or %NULL if not enough memory could be
+ * Return value: (nullable) (transfer full): the new #GdkPixbuf, or %NULL if not enough memory could be
  * allocated for it.
  **/
 GdkPixbuf *
diff --git a/gdk-pixbuf/gdk-pixbuf.c b/gdk-pixbuf/gdk-pixbuf.c
index c86d096..8f220f4 100644
--- a/gdk-pixbuf/gdk-pixbuf.c
+++ b/gdk-pixbuf/gdk-pixbuf.c
@@ -473,7 +473,7 @@ gdk_pixbuf_calculate_rowstride (GdkColorspace colorspace,
  * buffer has an optimal rowstride.  Note that the buffer is not cleared;
  * you will have to fill it completely yourself.
  *
- * Return value: A newly-created #GdkPixbuf with a reference count of 1, or 
+ * Return value: (nullable): A newly-created #GdkPixbuf with a reference count of 1, or
  * %NULL if not enough memory could be allocated for the image buffer.
  **/
 GdkPixbuf *
@@ -511,7 +511,7 @@ gdk_pixbuf_new (GdkColorspace colorspace,
  * @pixbuf. Note that this does not copy the options set on the original #GdkPixbuf,
  * use gdk_pixbuf_copy_options() for this.
  * 
- * Return value: (transfer full): A newly-created pixbuf with a reference count of 1, or %NULL if
+ * Return value: (nullable) (transfer full): A newly-created pixbuf with a reference count of 1, or %NULL if
  * not enough memory could be allocated.
  **/
 GdkPixbuf *