Expose m_flags in RayResultCallback

[LeXXik]

When a raytest is performed, it may return the backface hit result:

var rayCallback = new Ammo.AllHitsRayResultCallback(start, end);
dynamicsWorld.rayTest(start, end, rayCallback);

Exposing the flag on the callback allows us to set it so that the backfaces are ignored:

var rayCallback = new Ammo.AllHitsRayResultCallback(start, end);
rayCallback.set_m_flags(1 << 0);
dynamicsWorld.rayTest(start, end, rayCallback);