Reducing the buffer size of HTTPS responses broke DHT nodelist fetching. This change
puts the old buffer size back and converts all stack allocations of the read buffer
to heap allocations.
List is now automatically fetched from nodes.tox.chat and placed in the
user config directory. The list is updated once every 30 days, and
will attempt to detect problems and re-fetch the list if necessary.
Also fixed a couple file descriptor leaks and cleaned some things up.
