Log Message: 
Two modifications to OpenMP versioned AMG:
(1) in RungeStueben Search:
* use a smaller panel to reduce the searching time for an unkown with
the largest lambda value;
* fix the mistakes made in this function (Two places where set S is
expected, not set S^T).
(2) while construct the coarse level matrix A_C:
A_C = P^T (A P) where A is the fine level matrix and P is the
interpolation operator. Since we've already had the tranpose of P
when we process "A_temp = A P", the performance of matrix product
can be improved when we use P^T for the calculation of A_temp.
