Disabled DefaultType directive and removed ap_default_type()

from core.  We now exclude Content-Type from responses for which
a media type has not been configured via mime.types, AddType,
ForceType, or some other mechanism.  MMN major bump to NZ time.

PR: 13986



git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@739382 13f79535-47bb-0310-9956-ffa450edef68