tests: don't use deprecated fail_unless check API

It causes errors like this when running make check:

check_public.c:40:24: error: too many arguments for format [-Werror=format-extra-args]
   40 |   fail_unless(success, "unexpected parse failure %sfor '%s'", test_string[test_type], name);

Note: check 0.9.6 was released Dec 29, 2008.

Also some gitignore additions.

Fixes #49 (closed).