Worked around the failing CSV tests for PSv4 for now.

PowerShell's CSV parsing got a bit more lenient starting in v3 (which
isn't a bad thing – the two cases that failed here were things I
wouldn't really want as a user). Either we follow suit or ignore the
cases for now, but constantly-failing reference tests are a nuisance
for CI. And by now it's hard to come by machines with only PSv2.

Eventually the tests need a bit restructuring as well, I guess.
Currently it's a bit messy figuring out why a given test fails.