write()
chsize()

The DNS_blocking class supports the same API as the DNS class, but
does not use events, so any method will complete before returning.
As such, the callback argument is optional.

Updated usage/syntax help and comments too.

js_callback_t was not being properly retreived.

This allows for manual dupe checking against the index (returned by get_file_names()).

Incremented the copyright year to 2021.
Removed the juvenile ("hexor") CRC-protection of the copyright strings.

Fixes jsdoor builds for Windows.