Fix building of vcsbase on windows.

Change-Id: Iae5f31e0f86c3b27f23d5a453710e1d8e867a558
Reviewed-by: Hugues Delorme <delorme.hugues@fougsys.fr>

src/plugins/vcsbase/vcsplugin.h

@@ -44,7 +44,7 @@ QT_END_NAMESPACE
 namespace VCSBase {
 namespace Internal {
 
-struct CommonVcsSettings;
+class CommonVcsSettings;
 class CommonOptionsPage;
 class CoreListener;