Fixed build issues (boost issues #7979 and #8971)

The project was not compiling with gcc 4.8.2 on Ubuntu 14.04 because of:
* [Boost ticket #7979](https://svn.boost.org/trac/boost/ticket/7979)
* [Boost ticket #8971](https://svn.boost.org/trac/boost/ticket/8971)