Wholesale conversion to #pragma once

Kudos to cgmb and https://github.com/cgmb/guardonce

Change-Id: Ifa8970734b8d43fd08c9260c645bdb0228633791
Reviewed-by: Tobias Hunger <tobias.hunger@theqtcompany.com>

src/libs/qmljs/parser/qmljsgrammar_p.h

@@ -35,8 +35,7 @@
 //
 
 // This file was generated by qlalr - DO NOT EDIT!
-#ifndef QMLJSGRAMMAR_P_H
-#define QMLJSGRAMMAR_P_H
+#pragma once
 
 #include "qmljsglobal_p.h"
 #include <QtCore/qglobal.h>
@@ -196,5 +195,3 @@ public:
 
 
 QT_END_NAMESPACE
-#endif // QMLJSGRAMMAR_P_H
-