add an early note about the Pattern in a rewriterule behaving

counterintuitively in per-directory context. (lots of mysterious no-op 
rulesets due to ^/ in htaccess)

Tweak QSA text.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@832914 13f79535-47bb-0310-9956-ffa450edef68