CppTools: Clean up ProjectPart

Change-Id: Ia7969ceb52ffb25e7c63b24bc33b091001e9b50a
Reviewed-by: David Schulz <david.schulz@qt.io>

src/plugins/clangcodemodel/clangbackendipcintegration.h

@@ -36,6 +36,8 @@
 #include <QSharedPointer>
 #include <QVector>
 
+#include <functional>
+
 namespace Core {
 class IEditor;
 class IDocument;