Compute the value of Lagrange polynomial at given points

The function is implemented based on Barycentric method. The code is vectorized for fast speed. The mesh points x is a row vector. The mesh value y is a matrix, with each row representing the mesh values of a polynomial. y(i,j) is the value of the i'th polynomial at mesh points j. The return value p is a matrix, with p(i,j) to be the value of the i'th polynomial at points t(j)