If the content-length is zero, then we don't output the Content-Length

header file.  The only time that the C-L should be zero is if there is
no body.  Zero is a valid content-length, but the only time that we ever
really send it is on a HEAD request right now, and that is incorrect.
The HEAD response should have the actual content's length.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86953 13f79535-47bb-0310-9956-ffa450edef68