[boost] [config] config_test fails on g++ 4.8/4.9

... due to In file included from ../libs/config/test/config_test.cpp:376:0: ../libs/config/test/boost_no_lambdas.ipp: In function ???int boost_no_cxx11_lambdas::test()???: ../libs/config/test/boost_no_lambdas.ipp:21:4: error: expected primary-expression before ???void??? (void)[](){}; ^ ../libs/config/test/boost_no_lambdas.ipp:21:4: error: expected ???)??? before ???void??? I'm not sure why.