Changes since 0.2:
* provide usage message when called with invalid options
* moved do_test_default() from public API section in the source
* renamed private variables to not be in uppercase
* indented consistently
* replaced unnecessary ${VAR} with simple $VAR
* moved actual test execution into its own function
* when invoked with the -v option, announce which test will be run
as it's only used internally by bsd.prefs.mk.
* Make _PKGSRCDIR a public variable by renaming it to PKGSRCDIR.
Also, generate its value from ${_PKGSRC_TOPDIR} so it's less fragile
than the old method of stripping off the last two components of
${.CURDIR}. PKGSRCDIR may now be used after bsd.prefs.mk is defined.
* Change all references to _PKGSRCDIR to PKGSRCDIR.
Tests are found in pkgsrc/regress, tests are run by executing pkg_regress.
Based on an idea discussed at pkgsrcCon 2004. Thanks to dillo@ for review
and refinements, and to jlam@ for review.