Modified mod_mime and mod_negotiation to prevent mod_negotiation

Modified mod_mime and mod_negotiation to prevent mod_negotiation
from serving any multiview variant containing one or more
'unknown' filename extensions. In PR #8130, mod_negotiation was
incorrectly serving index.html.zh.Big5 when better variants were
available. The httpd.conf file on the failing server did not have
an AddLanguage directive for .zh, which caused mod_mime to loose
the file_type information it gleened from parsing the .html
extension. The absence of any language preferences, either in
the browser or configured on the server, caused mod_negotiation
to consider all the variants equivalent. When that occurs,
mod_negotiation picks the 'smallest' variant available, which
just happened to be  index.html.zh.Big5.
[Bill Stoddard, Bill Rowe] PR #8130

PR: 8130

git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/branches/1.3.x@91243 13f79535-47bb-0310-9956-ffa450edef68