darcs patch: Fix printing of 'impl' checks. (and 2 more)

Fri Aug 3 22:06:22 CEST 2007 Thomas Schilling * Fix printing of 'impl' checks. Fri Aug 3 22:08:29 CEST 2007 Thomas Schilling * Fix import path to HUnit. Fri Aug 3 23:33:31 CEST 2007 Thomas Schilling * Change error message for tabs used as indentation to something more helpful.