Move the <PRE> prefix for plaintext header files to before

	the header file emission, rather than before the page preamble.

PR:		1667
Submitted by:	John Van Essen <jve@gamers.org>
Reviewed by:	Dean Gaudet, Ken Coar, Jim Jagielski


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@79925 13f79535-47bb-0310-9956-ffa450edef68