This was due by reusing slabs from a terminated upload without reseting the
various parameters including the done parameter.

 * Added a content handler that overrides the original handler (but calls it). It is
used to add our own read_event_handler.

 * Implemented a read_event_handler that calls the original handler, and store the rest/content_length in our
own node.

 * modified the different handlers to use the new node fields

* added new CHANGES
* support for lowercase or mixed case X-Progress-ID header or parameter (fixes IE lowercasing headers)
* report original HTTP error code in probe in case of upload error
* fix crash reported by Michal Drapiewski

This version contains:
 * new timeout to remember connections after they are finished to be able
 to report termination on this connection to upload progress probes

 * handling of HTTP error 413 (request entity too large)

Addition of a header filter to track HTTP errors and return
the right status to upload progress probes.

This timer help us track finished connections and still report the status to progress probe.

* Added header filter to track 413 errors (not working atm)

 * First version