add BOOST_SPIRIT_THREADSAFE

Добавлен BOOST_SPIRIT_THREADSAFE для решения
https://github.com/novacoin-project/novacoin/issues/57
WindowsXP fix

fix для Windows XP.
Подробности здесь:
https://github.com/novacoin-project/novacoin/issues/52
Merge pull request #60 from fsb4000/fix-problems

Fix problems