[PATCH] ICAP 206 Partial Content extension

Hi all,
    This patch add support for the new ICAP 206 Partial Content extension.
This extension allows the ICAP agents to optionally combine adapted and
original HTTP message content.
For more information about ICAP Partial Content extension look at the
draft from the ICAP forum:

http://www.icap-forum.org/documents/specification/draft-icap-ext-partial-content-07.txt

The new configuration option "icap_206_enable" added to enable/disable
the 206 feature.

This is a Measurement Factory project.

Regards,
     Christos