Psionic focus blocks dual-wielding

[yufra]

If you are wielding a two-handed weapon in the PSIONIC_FOCUS slot then you cannot wield in the off-hand because of the slot_forbid flag in the PSIONIC_FOCUS slot. I have created a patch that removes the slot_forbid value when wielding using Telekinetic Grasp and restores it when you remove the weapon (either through Telekinetic Grasp or other means). I also did a quick check with Moon to ensure the original on_takeoff function is restored correctly (set slot_forbid to true, tracked the memory address before/during/after putting it in PSIONIC_FOCUS).