[glibmm] gmmproc: Put DOXYGEN_SHOULD_SKIP_THIS around *_Class prototypes.

[Murray Cumming <murrayc src gnome org>]

commit a3b4eeff1bb475d29f92fdfd2b2975274750e081
Author: Murray Cumming <murrayc murrayc com>
Date:   Tue Feb 3 12:49:14 2015 +0100

    gmmproc: Put DOXYGEN_SHOULD_SKIP_THIS around *_Class prototypes.
    
    These predeclarations, such as below, seem to confuse doxygen.
    See bug #743918 .
    
    namespace Gtk
    { class Window_Class; } // namespace Gtk

 tools/m4/class_gobject.m4   |    3 +++
 tools/m4/class_interface.m4 |    3 +++
 2 files changed, 6 insertions(+), 0 deletions(-)
---
diff --git a/tools/m4/class_gobject.m4 b/tools/m4/class_gobject.m4
index f097f18..14cbb22 100644
--- a/tools/m4/class_gobject.m4
+++ b/tools/m4/class_gobject.m4
@@ -115,7 +115,10 @@ ifdef(`__BOOL_NO_WRAP_FUNCTION__',`dnl
 _STRUCT_PROTOTYPE()
 ')dnl
 
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
 __NAMESPACE_BEGIN__ class __CPPNAME__`'_Class; __NAMESPACE_END__
+#endif //DOXYGEN_SHOULD_SKIP_THIS
+
 _SECTION(SECTION_HEADER3)
 
 ifdef(`__BOOL_NO_WRAP_FUNCTION__',`dnl
diff --git a/tools/m4/class_interface.m4 b/tools/m4/class_interface.m4
index fe4add6..fb6d387 100644
--- a/tools/m4/class_interface.m4
+++ b/tools/m4/class_interface.m4
@@ -117,7 +117,10 @@ define(`_END_CLASS_INTERFACE',`
 _SECTION(SECTION_HEADER1)
 _STRUCT_PROTOTYPE()
 
+#ifndef DOXYGEN_SHOULD_SKIP_THIS
 __NAMESPACE_BEGIN__ class __CPPNAME__`'_Class; __NAMESPACE_END__
+#endif // DOXYGEN_SHOULD_SKIP_THIS
+
 _SECTION(SECTION_HEADER3)
 
 ifdef(`__BOOL_NO_WRAP_FUNCTION__',`dnl