Axe unnecessary memset() calls and allocating an extra

byte in an I/O buffer for '\0', which hasn't been needed
since a strstr("\r\n\r\n") was removed in r371428.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@1591472 13f79535-47bb-0310-9956-ffa450edef68