gcc 4.9

This PR upgrades gcc to version 4.9 which was [released](http://gcc.gnu.org/gcc-4.9/) yesterday (22. April).
The [patch](http://gcc.gnu.org/ml/gcc-patches/2014-02/msg00477.html) for tiger is now merged into gcc 4.9, but I couldn't test the compilation on tiger, because I don't have such an old mac.