[CTX] [ALL] header replacement

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replace-[i][qr]head:name:body

replace headers of "name:" with "name:body" in forwarded request/response message. This is equivalent to the combination of kill-head and add-head.

Example:

HTTPCONF=replace-qhead:Referer:http://x.y.z
HTTPCONF=kill-qhead:Referer HTTPCONF=add-qhead:Referer:http://x.y.z

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