[gtk+] Expand the cursors demo text

[Matthias Clasen <matthiasc src gnome org>]

commit 08be6651d6c5ca63e5226d6f5d6a32082177fef5
Author: Matthias Clasen <mclasen redhat com>
Date:   Sun Nov 5 11:24:12 2017 -0500

    Expand the cursors demo text
    
    Explain what why we show each cursor 4 times.

 demos/gtk-demo/cursors.c |    5 ++++-
 1 files changed, 4 insertions(+), 1 deletions(-)
---
diff --git a/demos/gtk-demo/cursors.c b/demos/gtk-demo/cursors.c
index 39bf801..275dab0 100644
--- a/demos/gtk-demo/cursors.c
+++ b/demos/gtk-demo/cursors.c
@@ -1,6 +1,9 @@
 /* Cursors
  *
- * Demonstrates a useful set of available cursors.
+ * Demonstrates a useful set of available cursors. The cursors shown here are the ones
+ * defined by CSS, which we assume to be available.
+ *
+ * The example shows creating cursors by name or from an image, with or without a fallback.
  */
 
 #include <gtk/gtk.h>