ClangTools: Show also diagnostics from project's header files

Fixes: QTCREATORBUG-21452
Change-Id: I73c85224e142f4f1d08c9ada75fe8359ebf0f984
Reviewed-by: Ivan Donchevskii <ivan.donchevskii@qt.io>

src/plugins/clangtools/clangtoolsdiagnostic.cpp

@@ -38,5 +38,13 @@ bool Diagnostic::isValid() const
     return !description.isEmpty();
 }
 
+quint32 qHash(const Diagnostic &diagnostic)
+{
+    return qHash(diagnostic.description)
+         ^ qHash(diagnostic.location.filePath)
+         ^ diagnostic.location.line
+         ^ diagnostic.location.column;
+}
+
 } // namespace Internal
 } // namespace ClangTools