New partcombineUp and partcombineDown functions (issue 4514042)

[pkx166h]

When I try to patch to current tree (27 Aug) I get

--snip--
patching file lily/part-combine-iterator.cc
Hunk #2 succeeded at 138 with fuzz 1.
Hunk #4 FAILED at 390.
Hunk #5 FAILED at 412.
2 out of 5 hunks FAILED -- saving rejects to file
lily/part-combine-iterator.cc.rej
patching file ly/music-functions-init.ly
Hunk #1 succeeded at 762 (offset 29 lines).
patching file scm/part-combiner.scm
address@hidden:~/lilypond-git$

--snip--

Make succeeds though, and reg tests pass too.

So I have set this patch to 'review' as I don't know the significance of
these patch messages.

http://codereview.appspot.com/4514042/