INN warning cleanup

[Russ Allbery]

I made a push through the remaining warning issues in the CURRENT tree and
turned off some warnings in make warnings that were just too much of a
pain to try to use.  The result is that CURRENT now compiles almost free
of warnings with make warnings.  There are only a few structural things
that will require some more extensive work to correct.

Note that I've done this for the IPv6 path with Perl and Python enabled
and SASL enabled for imapfeed, so there may be other code paths that I've
not tested yet.

-- 
Russ Allbery (rra at stanford.edu)             <http://www.eyrie.org/~eagle/>

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