make PPI handle bytes, not codepoints
also use encoded content for PrereqScanner
make AutoPrereqs use the PPI role
warn about non-ASCII package or version

we pass these to PPI, which seems much happier with octets
than text
remove unneeded "use PPI"
pass the encoded content to abstract-extractor
require PPI as needed!
Assume that PPI wants octets, not text

The code:

  PPI->new($filename)

...opens files and reads them without an encoding layer.  I don't
care for this, but it's how it is.  The file's contents are
slurped and parsed.  Meanwhile:

  PPI->new(\$content)

...is parsed just the same as the slurped contents, indicating that
the content is bytes.  This branch tries to always pass bytes, not
character strings, to PPI.
changelog for next release
v5.009

        - include time offset by default in NextRelease
        - always pass PPI octets, not text