Try symlinks with an empty target

Show io phase name in error message.

use div/mod.

transferred".

I don't generally like changing that sort of thing, but I think this
one was a persistent source of confusion.

most frequently-used ones in here.

Nelson Beebe pointed out that the information about bug tracking was
out of date.

CPU on a local transfer, without achieving anything useful.

if we have not matched!

Drop unused variables.

Turn off -x.

handles different strings.

reduce symbol dependencies between files and therefore make it easier
to write unit tests.  The diff is large, but the actual code changes
are pretty small.

many places with a redirector to stderr.  If you just want to test a
particular routine you can link to this rather than the whole framework.