Final proxy cleanups for release. Change errant memchr call to memset.

Check for NULL read fd in proxy_send_fb() so we minimize risk of a coredump
after a timeout on the origin host connection.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@78237 13f79535-47bb-0310-9956-ffa450edef68