Avoid getting extra trailing whitespace from macros.

Avoid getting extra trailing whitespace from macros.

This trailing whitespace was coming from macro definitions and from
macro arguments. We fix this with a little extra state in the
token_list. It now remembers the last non-space token added, so that
these can be trimmed off just before printing the list.

With this fix test 23 now passes. Tests 24 and 25 are also passing,
but they probbably would ahve before this fix---just that they weren't
being run earlier.