kill -l requires the short version of the signal (without SIG prefix).

(apachectl graceful was broken.)

The best way to do this is to change configure to internally represent
the signal without the SIG prefix and prepend SIG before substitution
(and export a version without the SIG prefix for apachectl).

This highlights why we want to move apachectl's core functionality into
httpd.


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@91102 13f79535-47bb-0310-9956-ffa450edef68