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/qfilenameedit.h

@@ -1,25 +1,25 @@
 /*
 	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/>.
 */
 #ifndef Q_FILENAME_EDIT_H
 #define Q_FILENAME_EDIT_H
 #include <QLineEdit>
-#include <QRegExp>
 #include <QString>
+#include <QRegularExpression>
 class QETRegExpValidator;
 /**
 	This class represents a textfield dedicated to input a portable filename (not
@@ -31,7 +31,7 @@ class QETRegExpValidator;
 */
 class QFileNameEdit : public QLineEdit {
 	Q_OBJECT
-	
+
 	// constructors, destructor
 	public:
 	QFileNameEdit(QWidget * = nullptr);
@@ -39,22 +39,22 @@ class QFileNameEdit : public QLineEdit {
 	~QFileNameEdit() override;
 	private:
 	QFileNameEdit(const QFileNameEdit &);
-	
+
 	// methods
 	public:
 	bool isEmpty();
 	bool isValid();
-	
+
 	private:
 	void init();
 	void displayToolTip();
-	
+
 	private slots:
 	void validationFailed();
-	
+
 	// attributes
 	private:
-	QRegExp regexp_;
+	QRegularExpression regexp_;
 	QETRegExpValidator *validator_;
 	QString tooltip_text_;
 };