This serie starts moving type handling into PDB backend. In order to handle both the existing symt_{*} structures for every debug info objects and their potential counterpart inside a debug info backend, we introduce an opaque symref_t which can either hold a pointer or a value dedicated to a debug backend. This allows: - to have generic code handling transparently a debug info object (whether it's managed as a symt_{*} object, or as a reference in backend) - during the migration phase from old to new PDB backend, to select, by type of object, whether it's handled by old or new backend, hence allowing a migration scheme by type of object. This series mainly introduces the symref_t instead of the existing pointer to symt_{*}. -- https://gitlab.winehq.org/wine/wine/-/merge_requests/7811