Set the amount of seconds to sleep after each chunck that has been sent.
One can implement some sort of throttle through adjusting the
buffer size and the throttle delay.
With a setting of buffersize=25600 and throttledelay=1 HTTP_Download will
sleep a second after each 25 K of data sent.
Just be aware that if gzip'ing is enabled, decreasing the chunk size
too much leads to proportionally increased network traffic due to added
gzip header and bottom bytes around each chunk.