various UI related backports from trunk

git-svn-id: https://lmms.svn.sf.net/svnroot/lmms/branches/lmms/stable-0.4@2027 0778d3d1-df1d-0410-868b-ea421aaaa00d

include/group_box.h

@@ -39,7 +39,7 @@ class groupBox : public QWidget, public boolModelView
 {
 	Q_OBJECT
 public:
-	groupBox( const QString & _caption, QWidget * _parent );
+	groupBox( const QString & _caption, QWidget * _parent = NULL );
 	virtual ~groupBox();
 
 	virtual void modelChanged( void );