Remove the sendfile_handler (was #if 0'ed out) that does the buffer hi-jack

trick in order to send the headers out on the sendfile call. Besides, BUFF is
going away with brigades and filters...


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@86079 13f79535-47bb-0310-9956-ffa450edef68