Disable sorting for certain vector types

This patch is a second try to disable sorting for List, RawVector and ExpressionVector, as was discussed in #203 .

The trick here does not rely on C++11. Ideas are borrowed from #214 .

I ran a whole `R CMD check` on all packages depending on Rcpp. `clusteval` failed on a Lapack error that is not related to Rcpp, and I couldn't check the following packages due to lack of dependent libraries:
`classify`, `cqrReg`, `psgp`, `RcppOctave`, `RcppRedis`, `rpg`, `RProtoBuf` and  `surveillance`.

All others passed the check with possibly a few NOTEs that are also not an Rcpp issue.