[RFC] Allow all tests to pass with nocp

This is a follow up on #671. I can now run `make oldtest` with `nocompatible` without any errors.
The majority of lines in this test are of the form `:<command><tab><tab><tab><tab> " Comment` (i.e., "real" tabs) , which triggers the wildchar expansion. Setting the wildchar to the `cp` value is the minimal invasive edit, imo.

I'll come back to your other two comments, but I have to investigate first for myself (those were converted by klusark).