[PATCH 0 of 2] run-tests: add --debug option

[Greg Ward]

Resending my patch (from several months ago!) to add a useful
"run-tests --debug" mode.  The idea is to render obsolete the
'debug-tests' script that has been floated in the past.

This version is for discussion and review, not for pushing just yet.
(--debug should disable timeouts, but that doesn't work.  Or I forgot
to implement it, or somethinng stupid like that.)

        Greg