Define a "apache private" signal names list if the OS does not have one.

Note: Currently, this list is initialized at run-time.
Additionally, check valid range of siglist array in sig_coredump() routine.

Reviewed by:	Jim Jagielski, Dean Gaudet


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@81227 13f79535-47bb-0310-9956-ffa450edef68