Merge r1399708 from trunk:

only write the first len chars to syslog, as the buffer may have additional
text added speculatively

Submitted by: trawick
Reviewed/backported by: jim


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1408743 13f79535-47bb-0310-9956-ffa450edef68