fix n_x_point from linear interpolation and problem with psitbxtcv2 removing time points

integers should be piece-wise constant interpolated, and psitbxtcv2/psitbxtcv use unique(t) once closest times are taken, thus it removes time points if time_out array delta_t smaller than liuqe (which is easy since typically 17ms). At this stage modified psitbxtcv2/psitbxtcv with unique_t=false input arg in my matlab_imas folder