MIDI: reset channel counters when done; issue 1678 (issue4757043)

[pkx166h]

Passes Make tests - I still get:

--snip--
@ -1,8 +1,6 @@
 Parsing...
 Renaming input to:
`/home/jlowe/lilypond-git/input/regression/midi-volume-equaliser.ly'
 Interpreting music...
-warning: MIDI channel wrapped around
-warning: remapping modulo 16
 MIDI output to
`/home/jlowe/lilypond-git/build/out/lybook-testdb/f2/lily-c0ae894c.midi'...
 Writing header field `texidoc' to
`/home/jlowe/lilypond-git/build/out/lybook-testdb/f2/lily-c0ae894c.texidoc'...
 Layout output to
`/home/jlowe/lilypond-git/build/out/lybook-testdb/f2/lily-c0ae894c.eps'...

--snip--

I don't know if this fix is intended to resolve this (if not ignore this
:) ).

James

http://codereview.appspot.com/4757043/