abort on read failure

I was recently in an environment with a very weak connection.
With most sites, if I didn't get a full page, lsof would show the
connection still open and just sitting there. Some sites _would_
close the connection, but unfortunately dillo wouldn't give the
user any indication that further waiting was pointless.

I just committed some code that aborts the connection on read
failure. It also gives a status msg to the user (though status
messages are imperfect, as discussed last month).

The case where no data was received could bear further improvement,
but I had limited time and improved what I needed most.

It got a week or so of "free" testing in that bad environment,
and hasn't given me any trouble since then in more solid
environments.