Fix deprecated QRegExp

Use QRegularExpression instead.

https://doc.qt.io/qt-5/qregularexpression.html#notes-for-qregexp-users

This function was introduced in Qt 5

sources/diagramposition.h

@@ -1,17 +1,17 @@
 /*
 	Copyright 2006-2020 The QElectroTech Team
 	This file is part of QElectroTech.
-	
+
 	QElectroTech is free software: you can redistribute it and/or modify
 	it under the terms of the GNU General Public License as published by
 	the Free Software Foundation, either version 2 of the License, or
 	(at your option) any later version.
-	
+
 	QElectroTech is distributed in the hope that it will be useful,
 	but WITHOUT ANY WARRANTY; without even the implied warranty of
 	MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 	GNU General Public License for more details.
-	
+
 	You should have received a copy of the GNU General Public License
 	along with QElectroTech.  If not, see <http://www.gnu.org/licenses/>.
 */
@@ -19,7 +19,6 @@
 #define DIAGRAM_POSITION_H
 #include <QPointF>
 #include <QString>
-#include <QRegExp>
 /**
 	This class stores the position of an electrical element on its parent diagram.
 	While exact coordinates can be stored for convenience, the concept of diagram
@@ -31,7 +30,7 @@ class DiagramPosition {
 	public:
 	DiagramPosition(const QString & = "", unsigned int = 0);
 	virtual ~DiagramPosition();
-	
+
 	// methods
 	public:
 	QPointF position() const;
@@ -40,7 +39,7 @@ class DiagramPosition {
 	bool isOutOfBounds() const;
 	unsigned int number()const {return number_;}
 	QString letter()const {return letter_;}
-	
+
 	// attributes
 	private:
 	QString letter_;