Replace the Vary fixup code with a single-pass, single-copy

implementation that only adds the cost of a single ap_make_array
when there is no Vary field.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@83544 13f79535-47bb-0310-9956-ffa450edef68