Order's "temp" and "free" fields use NodeLists in a rather
non-idiomatic way.  Instead of using the "list" or "concat" functions,
it manipulates them directly and without the normal invariants (e.g.,
it doesn't maintain the "End" field).

Rather than convert it to more typical usage, just replace with a
slice, which ends up much simpler anyway.

Passes toolstash/buildall.

Change-Id: Ibd0f24324bd674c0d5bb1bc40d073b01e7824ad5
Reviewed-on: https://go-review.googlesource.com/19776
Run-TryBot: Matthew Dempsky <mdempsky@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Ian Lance Taylor <iant@golang.org>