Fixed bug #1142: Non-indexed but listed attributes issues diagnostic.

We keep the existing behavior by default and continue to issue a
diagnostic. Typically there are many attributes given in .att-files which
are never used in a Zebra installation. If they issue 0 hits, then
most Zebra servers will basically lie about their capabilities. It
would also confuse a lot of users.. (Dead programs tell no lies).
But it is certainly useful to be able to say "allow unknown use
attribtute" in controlled environments and in multi server systems
(where attributes may not indexed in all places) . Zebra now allows
attribute 14 to control this. 14=0 makes Zebra works as usual (throw
a diagnostic). 14=1 makes Zebra produce 0 hits (for the leaf/APT)