Qt: Fix Qt5 deprecation warnings

Mostly the warnings were about QString::sprintf and QFontMetrics::width.
sprintf replacement is asprintf, which annoyingly behaves differently
from sprintf - it seems to append to the string.

Not thoroughly tested, but seems to work.

win/Qt/qt_rip.cpp

@@ -36,7 +36,7 @@ tryload(QPixmap& pm, const char* fn)
 {
     if (!pm.load(fn)) {
 	QString msg;
-	msg.sprintf("Cannot load \"%s\"", fn);
+	msg = QString::asprintf("Cannot load \"%s\"", fn);
 	QMessageBox::warning(NetHackQtBind::mainWidget(), "IO Error", msg);
     }
 }