Added class groups example to Doxygen and added parent "Functions and Macros", and "Classes by Category" groups.

Also added CSS to add "Categories / " to the "Modules" tab label, and turned on DETAILS_AT_TOP setting.

git-svn-id: https://svn.wxwidgets.org/svn/wx/wxWidgets/trunk@52454 c3d73ce0-8a6f-49c7-b76d-6d57e0e08775

interface/dc.h

@@ -8,6 +8,7 @@
 
 /**
     @class wxDC
+    @ingroup group_class_dc group_class_gdi
     @wxheader{dc.h}
 
     A wxDC is a @e device context onto which graphics and text can be drawn.
@@ -977,6 +978,7 @@ public:
 
 /**
     @class wxDCClipper
+    @ingroup group_class_gdi
     @wxheader{dc.h}
 
     wxDCClipper is a small helper class for setting a clipping region on a