pmbasis linearized

[gilvillard]

New procedure nmod_poly_mat_pmbasis_linearized from nmod_poly_mat_pmbasis by changing the matrix multiplications involved.
Relies on new procedures for linearized matrix product.

Relies on #40 that seems to improve timings in the vast majority of cases.

• nmod_poly_mat_mul_linearized for a product A(x).B(x), linearizes the columns of B into chunks of length related to the degree of A (to be tuned);
• nmod_poly_mat_middle_product_linearized, uses nmod_poly_mat_mul_linearized;
• the product of intermediate bases relies on nmod_poly_mat_mul_geometric;
• the test for switching to mbasis is now (order <= (ipmat->r)) rather than if (order <= PMBASIS_THRES) (to be tuned).

The following tests give an idea of the range of superiority of nmod_poly_mat_pmbasis_linearized. A comparison is also made with nmod_poly_mat_middle_product_geometric as only modification in nmod_poly_mat_pmbasis.

pmbasis linearized.pdf

Rider: adding a .h that had been forgotten for some of the prototypes in maple.

[gilvillard]

See comment close to nmod_poly_mat_shift_right(BT, B, nlo-degA); in middle_product.c, problem over there, certainly (ASan check failed)