End "Left click" in the 3D game world.
- Flag (optional) - If present and set then any camera offset is 'sticky' and remains until explicitly cancelled.
- This function is called when left clicking in the 3-D world.
- When used alone, can cancel a "mouselook" started by a call to CameraOrSelectOrMoveStart.
- IMPORTANT: The normal restrictions regarding hardware event initiations still apply to anything this function might do.