In particular:
- Don't include none submitter buttons.
- Use type_state() instead type() to avoid direct string comparisons
- Support the hidden _charset_ input
- Get form associated element's value directly instead of via the value
attribute
- Split line break normalization into a separate function so that it
can also be used by form submission.
This makes use of the new [UseNewAKString] extended attribute. Using
Vector storage will make it easier to make this interface into an IDL
iterable. It seems the reason it didn't use Vector originally was due
to awkward DeprecatedString -> String conversions.
