Glk: new additions to Blorb and Dispatch layers

[ptomato]

There are some new functions in cheapglk's gi_blorb.h and gi_dispa.h` that aren't documented in the Blorb and Dispatch Layer appendices:

• giblorb_load_image_info()
• gidispatch_set_game_id_hook()
• gidispatch_get_game_id()
• gidispatch_set_autorestore_registry()

There's also the new Debug Layer in gi_debug.h.

What's the status of these, are they "official" enough that they should be documented in the appendices?