Also during this process, I felt necessary to slightly alter functions
prototypes (better name, easier usage/implementation).
I also specified the NULL terminated strings ownership, and thus
reworked some aspects of objects ownership.
NULL or empty strings usage also have been documented. For ROM, empty or
NULL strings allow to have an empty transferpak. For RAM, empty or NULL
strings will let the core generate a suitable save filename and
initialize it with empty content. This can be helpful when a GB save
file is not available and the game doesn't really care about the initial
saved content (for instance Perfect Dark).
The init_gb_cart function as also been slightly modified to better
handle loading failures (and not leak stuff in this case).
The GB pak switch function is now only activable when the game is
compatible with the Transferpak. Still you can change what is inside the
transferpak even when the transferpak is not plugged in.
