Boost libraries on windows are too much a hassle to handle, so thread safety is not worth all the trouble => think to move to c++11 thread support

include/assimp/defs.h

@@ -234,9 +234,9 @@ OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 	 * threads then and is itself not threadsafe.
 	 * If this flag is specified boost::threads is *not* required. */
 	//////////////////////////////////////////////////////////////////////////
-//#ifndef ASSIMP_BUILD_SINGLETHREADED
-//#	define ASSIMP_BUILD_SINGLETHREADED
-//#endif
+#ifndef ASSIMP_BUILD_SINGLETHREADED
+#	define ASSIMP_BUILD_SINGLETHREADED
+#endif
 
 #if defined(_DEBUG) || ! defined(NDEBUG)
 #	define ASSIMP_BUILD_DEBUG