[gdk-pixbuf] docs: Fix reference to a non-existent function

[Philip Withnall <pwithnall src gnome org>]

commit a4421926b2d7a40b6c1f36d46a88a93144f59c30
Author: Philip Withnall <philip tecnocode co uk>
Date:   Sat Jan 7 18:47:28 2017 +0000

    docs: Fix reference to a non-existent function
    
    That one moved to gdk-pixbuf-xlib a while ago.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=442452

 gdk-pixbuf/gdk-pixbuf-core.h |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)
---
diff --git a/gdk-pixbuf/gdk-pixbuf-core.h b/gdk-pixbuf/gdk-pixbuf-core.h
index d021ca1..a99cf4e 100644
--- a/gdk-pixbuf/gdk-pixbuf-core.h
+++ b/gdk-pixbuf/gdk-pixbuf-core.h
@@ -115,7 +115,7 @@ G_BEGIN_DECLS
  *  In the future it will do full alpha compositing.
  * 
  * These values can be passed to
- * gdk_pixbuf_render_to_drawable_alpha() to control how the alpha
+ * gdk_pixbuf_xlib_render_to_drawable_alpha() to control how the alpha
  * channel of an image should be handled.  This function can create a
  * bilevel clipping mask (black and white) and use it while painting
  * the image.  In the future, when the X Window System gets an alpha