Backport 1422234, 1416889, 1422253 from trunk:

const fixes for mod_imagemap.

Contributed By: covener, fuankg
Reviewed By: covener, fuankg, gsmith



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/2.4.x@1425750 13f79535-47bb-0310-9956-ffa450edef68