* server/log.c (piped_log_spawn): Return the APR error code,

as expected by piped_log_maintenance (and fixing "Unknown
error" messages in error path there).
(ap_open_piped_log): Expect an APR error code.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@170441 13f79535-47bb-0310-9956-ffa450edef68