merge from trunk and 2.2.x:

SECURITY: CVE-2010-0434 (cve.mitre.org)
Ensure each subrequest has a shallow copy of headers_in so that the
parent request headers are not corrupted.  Elimiates a problematic
optimization in the case of no request body.

PR: 48359
Submitted by: Jake Scott, William Rowe, Ruediger Pluem
Reviewed by: wrowe, trawick, rpluem



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.0.x@921910 13f79535-47bb-0310-9956-ffa450edef68