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.cpp

@@ -1,24 +1,24 @@
 /*
 	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/>.
 */
 #include "qfilenameedit.h"
 #include  "qetregexpvalidator.h"
 #include <QKeyEvent>
-#include <QRegExp>
+#include <QRegularExpression>
 #include <QToolTip>
 
 /**
@@ -36,7 +36,7 @@ QFileNameEdit::QFileNameEdit(QWidget *parent) : QLineEdit(parent) {
 */
 QFileNameEdit::QFileNameEdit(const QString &contents, QWidget *parent) : QLineEdit(parent) {
 	init();
-	if (!contents.isEmpty() && regexp_.exactMatch(contents)) {
+	if (!contents.isEmpty() && regexp_==QRegularExpression(contents)) {
 		setText(contents);
 	}
 }
@@ -61,7 +61,7 @@ bool QFileNameEdit::isEmpty()
 */
 bool QFileNameEdit::isValid()
 {
-	return(regexp_.exactMatch(text()));
+	return(regexp_==QRegularExpression(text()));
 }
 
 /**
@@ -69,7 +69,7 @@ bool QFileNameEdit::isValid()
 */
 void QFileNameEdit::init()
 {
-	regexp_ = QRegExp("^[0-9a-z_\\-\\.]+$", Qt::CaseSensitive);
+	regexp_ = QRegularExpression("^[0-9a-z_\\-\\.]+$");
 	validator_ = new QETRegExpValidator(regexp_, this);
 	setValidator(validator_);
 	tooltip_text_ = QString(