DGETRS solves a system of linear equations
    A * X = B  or  A**T * X = B
 with a general N-by-N matrix A using the LU factorization computed
 by DGETRF.

          TRANS is CHARACTER*1
          Specifies the form of the system of equations:
          = 'N':  A * X = B  (No transpose)
          = 'T':  A**T* X = B  (Transpose)
          = 'C':  A**T* X = B  (Conjugate transpose = Transpose)

          N is INTEGER
          The order of the matrix A.  N >= 0.

          NRHS is INTEGER
          The number of right hand sides, i.e., the number of columns
          of the matrix B.  NRHS >= 0.

          A is DOUBLE PRECISION array, dimension (LDA,N)
          The factors L and U from the factorization A = P*L*U
          as computed by DGETRF.

          LDA is INTEGER
          The leading dimension of the array A.  LDA >= max(1,N).

          IPIV is INTEGER array, dimension (N)
          The pivot indices from DGETRF; for 1<=i<=N, row i of the
          matrix was interchanged with row IPIV(i).

          B is DOUBLE PRECISION array, dimension (LDB,NRHS)
          On entry, the right hand side matrix B.
          On exit, the solution matrix X.

          LDB is INTEGER
          The leading dimension of the array B.  LDB >= max(1,N).

          INFO is INTEGER
          = 0:  successful exit
          < 0:  if INFO = -i, the i-th argument had an illegal value