Incorrect signature of `GrB_Matrix_diag`

[eriknw]

According to the GraphBLAS C API version 2.0.0, the signature for GrB_Matrix_diag should be:

1946 GrB_Info GrB_Matrix_diag(GrB_Matrix *C,
1947                          const GrB_Vector v,
1948                          int64_t k);

Note that this functions creates a new matrix C. This matrix is square with each dimension the size size(v) + |k| and the same datatype as v.

The first argument in SuiteSparse:GraphBLAS is currently GrB_Matrix C. Fwiw, I like GxB_Matrix_diag better.

[DrTimothyAldenDavis]

Fixed in v7.0.0, to be released shortly. I have conformed GrB_Matrix_diag to the spec.