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/plugins/debugger/qml/qmlv8debuggerclientconstants.h

@@ -23,8 +23,7 @@
 **
 ****************************************************************************/
 
-#ifndef QMLV8DEBUGGERCLIENTCONSTANTS_H
-#define QMLV8DEBUGGERCLIENTCONSTANTS_H
+#pragma once
 
 namespace Debugger {
 namespace Internal {
@@ -115,4 +114,3 @@ const char INTERNAL_FUNCTION[] = "(function(method) { "\
     "})";
 } //Internal
 } //Debugger
-#endif // QMLV8DEBUGGERCLIENTCONSTANTS_H