gmmNlWald — Wald test for GMM with nonlinear restrictions
rwd = gmmNlWald(rgmm,R,np)
rgmm = tlist result for unrestricted estimation
R = (s x 1) vector of nonlinear restriction of the form R(p)=0, example R=['p1-1/p2';'p5-p3*p4'];
np = 'noprint' if the user does not want to print the results
rwd a tlist with:
-rwd('chistat') = test statisitc
-rwd('pvalue') = pvalue of the test
-rwd('df') = number restriction