Mark command_rec and handler_rec as const... this is a backwards

compatible change, 3rd party modules shouldn't get any warnings or
anything due to it.  But the advantage is that a bunch more data goes
into read-only sections of memory and some systems can take advantage
of that by not duplicating the page across a fork().


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@80514 13f79535-47bb-0310-9956-ffa450edef68