Returns the gradient.
g=uncprb_getgrdfcn(n,m,x,nprob)
the number of variables, i.e. the size of x
the number of functions, i.e. the size of fvec
a n x 1 matrix of doubles, the point where to compute f
the problem number
a 1 x n matrix of doubles, the gradient
It is an interface function which calls the function func(which selects appropriate test fuction based on nprob) to return fvec and J then it calculates the gradient function's value.