Start using registered image/vnd.microsoft.icon type for ico

PR: 41035

There is some risk in this because it was registered for MS by
someone else, but most browsers ignore the type anyway.



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@571260 13f79535-47bb-0310-9956-ffa450edef68