support test output using the test anything protocol

support test output using the test anything protocol

Converts a test-result object into TAP format. Two new functions:
 * `write-tap`
 * `write-tap-to-file`

To manage the indentation levels TAP wants, this uses
[pprint-logical-block] and heavily uses the [~I] format directive,
which is shorthand for [pprint-indent].  This gets a little tricky
because indentation levels only take effect after a newline.

[pprint-logical-block]: http://www.lispworks.com/documentation/HyperSpec/Body/m_ppr_lo.htm
[~I]: http://www.lispworks.com/documentation/HyperSpec/Body/22_cec.htm
[pprint-indent]: http://www.lispworks.com/documentation/HyperSpec/Body/f_ppr_in.htm

refs #3