[Rd] reorder [stats] and reorder.factor [lattice]

[Deepayan Sarkar]

It was recently pointed out on the lists that the S-PLUS Trellis suite has
a function called reorder.factor that's useful in getting useful ordering
of factors for graphs. I happily went ahead and implemented it, but it
turns out that R (not S-PLUS) has a generic called reorder (with a method
for "dendrogram"). Naturally, this causes R to think I'm defining a
method for "factor", and gives a warning during check because of
mismatching argument names.

Any suggestions as to what I should do? Retaining S compatibility doesn't
seem to be an option. I could make a reorder method for "factor" (which
sounds like a good option to me), or rename it to something like
reorderFactor.

Deepayan