Upgrade Clang to 3.8 on Travis and use Clang's libc++.
Upgrade Clang to 3.8 on Travis and use Clang's libc++.

GCC 4.8's libstdc++ is incompatible with C++14 due to a build config
bug (see https://llvm.org/bugs/show_bug.cgi?id=18402).

padenot/cubeb,padenot/cubeb,kinetiknz/cubeb,padenot/cubeb,kinetiknz/cubeb,kinetiknz/cubeb