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/cmakeprojectmanager/configmodel.h

@@ -83,4 +83,3 @@ private:
 };
 
 } // namespace CMakeProjectManager
-