Add annotation for removing default constructor
Not all concrete types can, or should be available for construction:
- ancillary types that are managed by other types
- singleton types with a specific "static" function returning an instance
Various bindings will allow creating an instance of any non-abstract public type just by invoking
g_object_new(), which leads to interesting bugs.
A simple annotation for a class type like
no-default-constructor would allow bindings to warn/error when trying to instantiate a class.