[Livehttpheaders] patch to avoid content length mistakes

[Dustin Long]

Greetings,
I've attached a patch I've been using lately to help me from making 
mistakes when changing post content. It tries to find a content-length 
header in the http request and automatically updates it to match the 
post length. In the degenerate cases where I actually want the two to 
vary, it is always possible to manually edit the Content-Length header 
afterwards.

In general it has proved useful in helping me test most kinds of server 
issues. Perhaps you may find it useful to include this in the next release.

Regards,
Dustin