When the cache would validate 304 responses from back-end server, it would

When the cache would validate 304 responses from back-end server, it would
incorrectly set the content-length value to 0 (from the 304 response)
instead of keeping the original value.

PR: Bugz 10128
Obtained from:
Submitted by:	Paul Terry <paul.terry@gmx.net> and  ast@domdv.de
Reviewed by:

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@96647 13f79535-47bb-0310-9956-ffa450edef68