Utils: Remove function wrapper

This was an intentional, time-limited workaround that has
served its purpose now that we require C++11.

Change-Id: I96ece9c21bd405d281fd381bd9b87edc00c5ee84
Reviewed-by: Daniel Teske <daniel.teske@digia.com>
Reviewed-by: Fawzi Mohamed <fawzi.mohamed@digia.com>

src/plugins/cpptools/cppsourceprocessor.h

@@ -5,7 +5,6 @@
 
 #include <cplusplus/PreprocessorEnvironment.h>
 #include <cplusplus/pp-engine.h>
-#include <utils/function.h>
 #include <utils/qtcoverride.h>
 
 #include <QHash>
@@ -13,6 +12,8 @@
 #include <QSet>
 #include <QStringList>
 
+#include <functional>
+
 QT_BEGIN_NAMESPACE
 class QTextCodec;
 QT_END_NAMESPACE