Make some error checking more clear by using the defined constants instead

of literal values.

Patch by: Dan Rall <dlr apache.org>

* server/request.c
  (ap_process_request_internal): Check the return value of hook functions
   against the constant OK instead of the magic number 0 to improve clarity.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@368505 13f79535-47bb-0310-9956-ffa450edef68