Trac 16803: Added rel tol to doctest.
Trac #16803: Reimplement matrix_integer_dense using FLINT

In this ticket we reimplement all of matrix_integer_dense using FLINT
fmpz_mat_t.

The speed-up is substantial. With the new code:

{{{
sage: A = Matrix(ZZ,1000,1000,range(10^6))
sage: %time B = A*A
CPU times: user 883 ms, sys: 3.33 ms, total: 887 ms
Wall time: 888 ms
}}}

This takes more than 1 minute in the same computer using Sage 6.3.

URL: http://trac.sagemath.org/16803
Reported by: mmasdeu
Ticket author(s): Marc Masdeu
Reviewer(s): William Stein, Jeroen Demeyer