Remove usage of deprecated Qt API

Removes usage of the following deprecated Qt functions:
- QPixmap::grabWidget
- QString::null
- qFind
- qSort
- qGreater
- qCopy

plugins/patman/patman.cpp

@@ -78,7 +78,7 @@ PLUGIN_EXPORT Plugin * lmms_plugin_main( Model *, void * _data )
 
 patmanInstrument::patmanInstrument( InstrumentTrack * _instrument_track ) :
 	Instrument( _instrument_track, &patman_plugin_descriptor ),
-	m_patchFile( QString::null ),
+	m_patchFile( QString() ),
 	m_loopedModel( true, this ),
 	m_tunedModel( true, this )
 {
@@ -182,7 +182,7 @@ void patmanInstrument::setFile( const QString & _patch_file, bool _rename )
 {
 	if( _patch_file.size() <= 0 )
 	{
-		m_patchFile = QString::null;
+		m_patchFile = QString();
 		return;
 	}
 

plugins/vibed/nine_button_selector.cpp

@@ -52,8 +52,8 @@ nineButtonSelector::nineButtonSelector(	QPixmap _button0_on,
 					int _x, int _y,
 					QWidget * _parent ):
 	QWidget( _parent ),
-	IntModelView( new nineButtonSelectorModel(0, 8, _default, NULL, 
-				QString::null, true ), this )
+	IntModelView( new nineButtonSelectorModel(0, 8, _default, NULL,
+				QString(), true ), this )
 {
 	setFixedSize( 50, 50 );
 	move( _x, _y );