in calc, make anss, ansss, etc, up to 5

Start saving 5 histories of users' last answers in `^calc` instead of just 1, and have them keyworded as `ans` for the first one, then `anss`, then `ansss`, etc.

I guess we can also make `ans`, `ans2`, etc, through `ans5`.

Also, once this is set up, add global aliases `^anss` for `^calc anss` (and I guess `^ans2`) etc.