It means you can no longer modify eg parv[1] in-place with strtoken and such.
The main reason for this is that as a command handler you have no idea
where the arguments may come from. It could be from a do_cmd() with
read-only storage (eg a string literal) and so on.
It started with an experiment of how far I could get and how annoying the
side-effects would be, but they seem to be quite managable, so I'm
committing this stuff.
Hopefully this catches/solves some stupid bugs somewhere :)
Bram Matthys