Added new test file for (S)EP. For an autoregressive process SEP and EP should give the same results...

tests/ep/ar.mod

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+var Efficiency, efficiency;
+
+varexo EfficiencyInnovation;
+
+parameters rho, effstar, sigma2;
+
+/*
+** Calibration
+*/
+
+
+rho     =  0.950;
+effstar =  1.000;
+sigma2  =  0.0001;
+
+external_function(name=mean_preserving_spread);
+
+model(block,bytecode);
+
+  // Eq. n°1:
+  efficiency = rho*efficiency(-1) + EfficiencyInnovation;
+
+  // Eq. n°2:
+  Efficiency = effstar*exp(efficiency-mean_preserving_spread(rho));
+
+end;
+
+shocks;
+var EfficiencyInnovation = sigma2;
+end;
+
+steady;
+
+options_.ep.verbosity = 0;
+options_.ep.stochastic = 0;
+options_.console_mode = 0;
+
+
+ts = extended_path([],1000);
+
+
+options_.ep.verbosity = 0;
+options_.ep.stochastic = 1;
+options_.console_mode = 0;
+
+sts = extended_path([],1000);
+
+
+if max(max(abs(ts-sts)))>1e-12
+   disp('Stochastic Extended Path:: Something is wrong here (potential bug in extended_path.m)!!!')
+end

tests/ep/ar_steadystate.m

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+function [ys, info] = ar_steadystate(ys, exogenous)
+% Steady state routine for ar.mod (First order autoregressive process)
+    
+global M_
+    
+info = 0;
+
+ys(1)=M_.params(2);
+ys(2)=0;