Stop loading DFS

[ojwb]

Currently the bot loads DFS, which seems entirely useless but raises PAGE by 2816 bytes. Even in the best case of MODE7 and rocket mode, that's a 10% reduction in the available RAM to BBC BASIC. In MODE2 and with the GXR loaded it's a whopping 35% reduction.

I've butted up against this restriction and been annoyed by it multiple times, but I didn't propose changing it before as doing so would break programs which assume the value of PAGE (and while you really shouldn't assume the value of PAGE in general, in the context of squeezing the most out of every byte of code for the bot it's often handy to do so).

However the move to mastodon gives us a good opportunity to reconsider this - it seems more reasonable that existing programs from the bot may not work unmodified in this brave new world.

If there are some genuine uses for having DFS loaded (or if we just want to provide a simple way to run old programs which assume PAGE without reworking them), we could support a floppy disk emoji to reenable it.

Happy to provide a patch, though that really requires git to be up to date.