http get now uses two timeout values: one for the max time since last
server response, and one for total download time.
When AC is waiting for a server response (before a http header was
received), the progress bar will show the timeout "completion".
* based on the enet socket layer
* supports redirects, range requests and gzip encoding
* automatically tries to re-use existing connections
* easy multithreading
* writes output to file or ram buffer
