Example program for dpbrfs

This example solves the system of equations AX=B using iterative refinement and to compute the forward and backward error bounds, where
A= 5.49 2.68 0.00 0.00 2.68 5.63 -2.39 0.00 0.00 -2.39 2.60 -2.22 0.00 0.00 -2.22 5.17   and   B= 22.09 5.10 9.31 30.81 -5.24 -25.82 11.83 22.90 .  
Here A is symmetric and positive definite, and is treated as a band matrix, which must first be factorized by dpbtrf.