Integrate perlio:

[ 17159]
Tune test to run in UTF-8 locales
- test file must be opened as :bytes or high-bit octets
will be UTF-8 encoded on write in such locales, so
will not read as expected.
p4raw-link: @17159 on //depot/perlio: f2bb49b68cb535c8bc5ed120954660e49ab7d44b

p4raw-id: //depot/perl@17162