ICHOL: Added parallel incomplete Cholesky factorization by Chow and Patel.

Proposed by Chow and Patel in SIAM J. Sci. Comp. Vol. 37, No. 2, pp. C169–C193, 2015
in Algorithm 3. Rather than a column-major computation of U,
we compute the row-major L. This saves at least one (costly) transposition.