Fix Krazy warnings about includes/header guards in Cpp-Editor.

Change-Id: I00a68d7f2b509e3934c3248765a78e9b47749127
Reviewed-by: Nikolai Kosjar <nikolai.kosjar@digia.com>

src/plugins/cpptools/cppdoxygen.h

@@ -27,6 +27,9 @@
 **
 ****************************************************************************/
 
+#ifndef CPPDOXYGEN_H
+#define CPPDOXYGEN_H
+
 #include "cpptools_global.h"
 
 QT_FORWARD_DECLARE_CLASS(QChar)
@@ -260,3 +263,4 @@ CPPTOOLS_EXPORT const char *doxygenTagSpell(int index);
 
 } // namespace ::CppTools
 
+#endif // CPPDOXYGEN_H