debug logging to a file

[teuben]

The current "debug=2" would show levels 2 and below to the screen. It can be cumbersome to redirect to a file, e.g.

   program ... debug=2  2>p2.log

so perhaps it might be useful to have an option "debug=2,p2.log" which effectively does the same

   program ... debug=2,p2.log

The danger of using pipes is now that the order of debug output can (and will) be out of order.