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

docs/doxygen/wxwidgets.css

@@ -491,5 +491,7 @@ SPAN.style, SPAN.event {
     color: #880000;
 }
 
-
+A[HREF="modules.html"] SPAN:before {
+    content: "Categories / ";
+}