The standard states (8.3.6/4) that adding default arguments in later
function declarations are only valid for non-template functions.
In matrixmarket.hh, the function template loadMatrixMarket is declared
and a default argument for the last parameter is provided. In
owneroverlapcopy.hh, OwnerOverlapCopyCommunication contains a friend
declaration of loadMatrixMarket without the default parameter. If now
owneroverlapcopy.hh is included before matrixmarket.hh, the friend
declaration is the first declaration and the default parameter in
matrixmarket.hh is invalid.
By including matrixmarket.hh in owneroverlapcopy.hh, we make sure that
the declaration which provides the default argument is always the first
one.