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/diagramcontext.cpp

@@ -1,24 +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/>.
 */
 #include "diagramcontext.h"
-#include <QRegExp>
 #include "qet.h"
 #include <QDebug>
+#include <QRegularExpression>
+#include <QRegularExpressionMatch>
 
 /**
 	@brief DiagramContext::add
@@ -241,8 +242,9 @@ bool DiagramContext::stringLongerThan(const QString &a, const QString &b) {
 */
 bool DiagramContext::keyIsAcceptable(const QString &key) const
 {
-	QRegExp re(DiagramContext::validKeyRegExp());
-	return(re.exactMatch(key));
+	QRegularExpression re(DiagramContext::validKeyRegExp());
+	QRegularExpressionMatch match =re.match(key);
+	return match.hasMatch();
 }
 
 QDebug operator <<(QDebug debug, const DiagramContext &context)