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/gitclient.h

@@ -68,7 +68,7 @@ namespace Internal {
 class GitPlugin;
 class GitOutputWindow;
 class GitCommand;
-struct CommitData;
+class CommitData;
 struct GitSubmitEditorPanelData;
 class Stash;