binding to BLAS limit dimensions to 2^31

[pascalgiorgi]

There is a generalised issue with the call to BLAS functions. All FFLAS-FFPACK functions use size_t as the primary type for dimensions (i.e. vector, matrix) while BLAS uses int. Therefore, when functions are mapped down to BLAS, the cast to int causes limitation to 2^31. This is for instance the case with fassign for Modular. Note that there are no warnings neither errors that are raised.