Update array parameter names for named parameters

Update array parameter names for named parameters

* The array "subject" of a function gets called $array.

* Further parameters should be self-descriptive if used
  as a named parameter, and a full word, not an abbreviation.

* If there is a "bunch more arrays" variadic, it gets
  called $arrays (because that's what was already there).

* A few functions have a variadic "a bunch more arrays,
  and then a callable", and were already called $rest.
  I left those as is and died a little inside.

* Any callable provided to an array function that acts
  on the array is called $callback. (Nearly all were already,
  I just fixed the one or two outliers.)

* array_multisort() is beyond help so I ran screaming.