This updates the signature of `RNA_def_property_update_runtime`
which previously just has a `const void *` input. This made it difficult
to know what function signature is expected and also does not result
in compile errors when a wrong function is provided.
There is one case which required a different signature, so now there
is a separat function for that case.
While these warnings point to real errors in the code,
PyMethodDef are an exception where functions with different numbers
of arguments are all cast to the same function type.
