Merge pull request openscad#2465 from t0b1as/patch-3

Fix QSound include.

Author: t-paul

src/mainwin.cc

@@ -96,7 +96,7 @@
 #include "QWordSearchField.h"
 #include <QSettings> //Include QSettings for direct operations on settings arrays
 #include "QSettingsCached.h"
-#include <QtMultimedia/QSound>
+#include <QSound>
 
 #if (QT_VERSION < QT_VERSION_CHECK(5, 0, 0))
 #include <QTextDocument>