[boost] [C++11] Is conditional code allowed?

I am working on bugs in boost phoenix. I have found some problems eg. #7624 which run fine with C++11 with either Clang 3.4 or gcc 4.8.2. I also have a patch which has been suggested for bug #8704 which uses C++11. Is there a way to incorporate C++11 only code into tests or the actual headers. If so, is there an example of how to do it in Boost? Thank you John Fletcher