As memtioned when I announced release 0.6.7 of Rcpp two days ago, a new version 0.6.8 was due because of my oversight of also adapting
Makevars.win(used on that other OS) to the new file layout.
So 0.6.8 went onto CRAN and into Debian earlier in the day. Beside the aforementioned fix, I also split off a more class headers and implementations into their own files but changed no actual functionality.
As always, more details are at the Rcpp page.