This is kind of a hack that circumvents the problem that Doxygen cannot
“see” an access via a std::unique_ptr when it generates the call graphs.

To do that, the file canbusconnection.cpp is passed through sed which
replaces the character sequence “_impl->” by
“CanBusConnectionImplementation”.

The result is valid C++ code and allows doxygen to understand which
methods of the implementation class is called.

Nevertheless, that code would not compile because the methods are not
static and need an instance. But for the purpose of generating call
graphs this does not matter and the original code is shown in the source
code listing, so everything is fine.