Re: [AD] destroy_bitmap after allegro_exit

[Javier González <xaviergonz@xxxxxxxxxx>]

> Javier's suggestion about passing NULL for `atexit_ptr' to
> `install_allegro' is good, but not backwards compatible.  If
> `atexit_ptr' is NULL `install_allegro' uses `atexit' by default
> (although this is not documented).
>
> But, of course, you can just pass a dummy `atexit' function.
> Problem solved :-)

Hmm, I don't see why to support an undocumented behaivour =)
In anyway, who expects (at least not me) than when NULL is passed it will
use by default atexit?

Could we change it to not call anything if NULL is passed? I ask for it
because
making an empty function just looks, uh... dummy =)