Add option to show disabled targets in the configuration dialog.

Note that disabled targets support is not intended for use by end users.
This is to make development (and testing of svn) easier and should get
disabled for releases.

git-svn-id: svn://svn.rockbox.org/rockbox/trunk@24513 a1c6a512-1295-4272-9138-f99709370657

rbutil/rbutilqt/base/systeminfo.h

@@ -65,6 +65,7 @@ class SystemInfo : public QObject
 
         enum PlatformType {
             PlatformAll,
+            PlatformAllDisabled,
             PlatformBase,
             PlatformVariant
         };