No more HOWTOBIND flags, and some optimisations

I used to have HOWTOBIND flags, but I didn't really understand what they did.
They're now gone. Phew!

A few more segfaults have been fixed.

I have also had a look at list.c, which was one of the very first things
I wrote for this project, and I have looked at implementing some obvious
optimisations in it.