Merge r326130 from trunk:

Proxy docs changes:

- Move ftp-related questions to mod_proxy_ftp.

- Document the proxy-sendcl and proxy-sendchunked env variables.

- Improve the docs on the other proxy env variables.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.2.x@326131 13f79535-47bb-0310-9956-ffa450edef68