Explicitly include vector.

Always explicitly include any library headers needed in a translation unit.
Use make_shared.
Mac OS X does not have pthread_spin_lock. Use OSSpinLock instead.
'init_priority' attribute is not supported on Mac OS X.
Merge pull request #12 from krzysztofwos/master

Get sodium C++ library to build on Mac OS X
Merge branch 'master' into c++03-support
More progress with C++03 support.