As per PR 44135

Feeling brave mucking with the rewrite docs =) 

setenvif -> added link to rewrite.html#rewritecond
rewrite -> added a see also so the rewrite flags stood out a little more.  



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@619726 13f79535-47bb-0310-9956-ffa450edef68