append, concatenate, and reverse for cons lists

[obriencj]

add methods for appending-to and reversing cons lists. These should mutate, not produce a new cons list. They should also work with improper and recursive lists.

[obriencj]

pair.append (mutates)
pair.copy-append (copy)
pair.reversed (copy)
pair.reverse (mutates)

[obriencj]

while we're in there, let's also add a pair.extend and a pair.copy-extend