Stop always allocating 8k for each request. We now count the number

Stop always allocating 8k for each request.  We now count the number
of bytes required for the headers for each request, and we just allocate
that number of bytes plus 100 extra.  The extra 100 are a fudge factor,
because it is a bit difficult to compute the exact length for the
basic HTTP headers like date and the status line.

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86781 13f79535-47bb-0310-9956-ffa450edef68