Modify the proxy to use tables instead of array_headers for header lines.

That simplifies some code, but changes many of the proxy-internal interfaces.
It should also prevent the proxy from merging multiple "Set-Cookie:" headers
into one.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@81938 13f79535-47bb-0310-9956-ffa450edef68