[gtk+/gtk-2-22] Document GSEAL_ENABLE with other preprocessor symbols. (cherry picked from commit 747c834f27d2c166ff

[Matthias Clasen <matthiasc src gnome org>]

commit c81abfae024e9fd7f174ffe9250f70e4049d28be
Author: Matthias Clasen <mclasen redhat com>
Date:   Fri May 21 22:07:46 2010 -0400

    Document GSEAL_ENABLE with other preprocessor symbols.
    (cherry picked from commit 747c834f27d2c166ffa2c0b3b9dc0e467aff3578)

 docs/reference/gtk/compiling.sgml |    9 +++++++++
 1 files changed, 9 insertions(+), 0 deletions(-)
---
diff --git a/docs/reference/gtk/compiling.sgml b/docs/reference/gtk/compiling.sgml
index a9a3632..c5e58b7 100644
--- a/docs/reference/gtk/compiling.sgml
+++ b/docs/reference/gtk/compiling.sgml
@@ -81,5 +81,14 @@ The same for <filename>gtkunixprint.h</filename> if you use the non-portable
 <link linkend="GtkPrintUnixDialog">GtkPrintUnixDialog</link> API.
 </para>
 
+<para>
+The next major version, GTK+ 3,  will remove many implementation details and
+struct members from its public headers. To ensure that your application will
+not have problems with this, you can define the preprocessor symbol
+GSEAL_ENABLE. This will make the compiler catch all uses of direct access to
+struct fields so that you can go through them one by one and replace them with
+a call to an accessor function instead.
+</para>
+
 </refsect1>
 </refentry>