Added informative error messages for failed munmap() and fseek() calls

in http_core.c.

Submitted by:	John Bley <jbb6@acpub.duke.edu>, Roy Fielding


git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@82872 13f79535-47bb-0310-9956-ffa450edef68