avoid "wide character" warning when printing non-ascii sub names

[karenetheridge]

closes Test-More/test-more#1031

[Grinnz]

I don't think this is the best way to manipulate TAP output which relies on STDOUT, but I suppose it depends how Test::Pod::Coverage works.

[karenetheridge]

I suppose we could do use Test2::Plugin::UTF8; instead, but that would force Test2 into the distribution -- albeit only for author tests, so maybe that's not a big deal.

[Grinnz]

True, and it is a core module in recent Perls, but given the complication of injecting dependencies it's probably not worth it here. I would however suggest doing it this way so it is specifically targeted to STDOUT (assuming the relevant characters are in the TAP stream output):

{ use open ':std', OUT => ':encoding(UTF-8)' }