schmiphi_tab — critical values for the Schmidt-Phillips statistic
[critical1,critical2]=schmiphi_tab(p,T)
p: order of the polynomial trend
T: # of observations
critical1: (1% - 2.5% - 5% -10%) critical values of the rho test
critical2: (1% - 2.5% - 5% -10%) critical values of the tau test