Add the ShmemUIDisUser directive and logic. Apache does not require

Add the ShmemUIDisUser directive and logic. Apache does not require
that the SysV shared memory segment be reset to the uid/gid of
User/Group. In fact, it's not wise that it do so. However, there are
some 3rd party "add ons" that require/expect this behavior...
So allow admins to do so, assuming they know the impacts.
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git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@96941 13f79535-47bb-0310-9956-ffa450edef68