purecopy-car and purecopy-cons

[Stefan Monnier]

I'd rather not introduce such functions:
- they're completely useless to non-maintainers.
- they're just one-liners.
- they waste (negligible) memory in Emacs after the dump, even though
  they're completely useless at that point.
- their name doesn't make it clear what they do, so you need to look up
  their definition when they're used, whereas the corresponding lambda
  expression is crystal clear.


        Stefan