Fix ambiguous encoding of data sections

All data sections are read raw and then decoded line by line.  This is
important to avoid reading with different layers depending on the utf8
pragma (or heavens forfend, the encoding pragma).

The default encoding is UTF-8, but may be modified by an 'encoding'
option provided as an import argument.

There is no support for section-specific encodings because I can't
imagine how anyone could get their editor to actually do that and not
royally screw it up.

The t/lib/Latin1.pm file is Latin1 encoded and will need special
treatment once dzil learns about encodings.  :-)