The version of callOnPathSteps without an actual instance was completely
ignoring the upcasted type of `UpcastablePointer`s. We now fix this by
calling the right template specialization, which we choose by inspecting
the key of the `UpcastablePointer`.
Model classes are now described by a YAML document, which is used to
generate C++ headers containing classes and all the boilerplate
required for YAML serialization/deserialization, usage in
SortedVectors, etc. See the README in include/revng/Model for more
info.
Before this commit, it was only matched by types that satisfied the
constraint `IsUpcastablePointer`, which is too strict.
Now also types that match `UpcastablePointerLike` satisfy the
constraints for this concept.
Massimo Fioravanti