back port this from 2.1-dev:

  mod_isapi: send_response_header() failed to copy status string's
  last character.

PR:		20619
Submitted by:	Jesse Pelton <jsp pkc.com>
Reviewed by:	trawick, stoddard, nd


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/APACHE_2_0_BRANCH@103773 13f79535-47bb-0310-9956-ffa450edef68