Use classes in favor of structs

Change-Id: I6ad2df70b7ad9b5fdc5baddc3ef85d0fed0c139c
Reviewed-on: http://codereview.qt.nokia.com/2518
Reviewed-by: Qt Sanity Bot <qt_sanity_bot@ovi.com>
Reviewed-by: Tobias Hunger <tobias.hunger@nokia.com>

src/plugins/git/gitplugin.h

@@ -74,8 +74,8 @@ class GitVersionControl;
 class GitClient;
 class ChangeSelectionDialog;
 class GitSubmitEditor;
-struct CommitData;
-struct GitSettings;
+class CommitData;
+class GitSettings;
 class StashDialog;
 class BranchDialog;
 class RemoteDialog;