Revert "Using C++11 threads to control the server service"

This reverts commit 15671a607e39d9e5c875ec79f043651323be12e2.

Using std::threads actually introduces more issues wrt using
boost::threads. In fact it happens that compiling code using std::thread
on linux with GCC requires passing the flag `-pthreads`. So instead of
manually managing platform differences it's better to use Boost as a
bridge to the actual platform at the price of adding one more
dependency (i.e. linking against boost::threads).
Using plain char[] instead of std::array

Clang on linux fails to compile.