Add logic to read the Upgrade header and use it in the response.
Use we you are proxying to a server that has multiple upgrade on the same IP/Port.
PR 61142

Submitted by: jfclere
Reviewed by: jfclere, jim, covener


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1808698 13f79535-47bb-0310-9956-ffa450edef68