Update cld2.R

[moodymudskipper]

Old name _multi was still used in doc. Replaced by new name _mixed.

[moodymudskipper]

ooops, previous pull request was doing exactly the same. But it's old and was apparently ignored, anybody around :)?

[jeroen]

You need to run roxygen2::roxygenize() to actually update the manual page.

[jeroen]

Oh haha, the old one has a merge conflict now, we'll just use yours.