ICAP related preview mode patch

Hi,

we are developing ICAP daemon for checking web content against viruses
(drweb-icapd). everything is OK except when we use preview mode.

explanation in details:

there are some bugs when drweb-icapd asks squid to stop transferring
content to drweb-icapd but allows to pass document to client at the time
before squid have got entire document from http server (think of stream
content - video, audio).

furthermore, if ICAP daemon does not support persistent connection and
answers with 'Connection: Close' squid can stop receiving the document from
a network and send the cut (without the ending) document to the client.

so, we offer the attached patch to solve these problems hoping it'll be
interesting not only for us. our developers with great pleasure will answer
to any your question.

-- 
Yours sincerely, Eugeny.
Doctor Web, Ltd. http://www.drweb.com