Fixing two issues

[kibaekkim]

I have found and fixed two issues.

The first issue is that member variable xDiag is not initialized and can potentially be undefined if nxlow + nxupp == 0 (that is, all variables are unbounded). This has been fixed in files sLinsysRoot.*. The initialization is safe because xDiag will be overwritten if nxlow + nxupp > 0. Please, however, make sure that xDiag is initialized with the right data.

The second issue is the assumption in the code that the matrix inputs are always column-ordered. This has been fixed in file sTreeImpl.C.