CTR: documentation

Merged r1526470 from tomcat/tc7.0.x/trunk:
Fix broken link to HTTP connector in the Proxy HowTo, as reported on the users list.

git-svn-id: https://svn.apache.org/repos/asf/tomcat/tc6.0.x/trunk@1553414 13f79535-47bb-0310-9956-ffa450edef68