[Csnd-dev] sysdep.h and MAXLEN for ftables

Hi All,

I was chatting with Giovanni Bedetti on Discord about max table length. It
seems awfully small at 2^24 (~16MB). Any reason not to bump that up to
something larger?

Also, while looking at that, I noticed B64BIT detection in sysdep.h. I saw
that it was missing aarch64 amongst other things, so I've submitted a PR to
update this.

steven