[boost] [range] Time to merge Oven-to-Boost Extensions?

Hi, IIRC, the formal review is not necessary for the merge of Akira's Oven-to-Boost Extensions; only the range authors' review/permission are necessary. Neil, Nate, could we merge the extensions in the near future? I think everyone wants * `dropped` adaptor * `elements` adaptor * `taken` adaptor * `regular` utility so merging these first (and eventually merging the rest) would make the users happy. Regards, Michel