#4 equal incorrect for interval types

[Michael Stevens]

"Guillaume Melquiond
guillaume.melquiond@ens-lyon.fr"
At lines 620-621, 688-689, 753-754 of ublas/traits.hpp
in the
equals function, uBLAS should not be using the norm_inf
function. Indeed
norm_inf relies on abs(interval); and what is really
needed is a
norm_inf_for_equals function that would rely on
norm(interval). The same
problem will also appear later with complex intervals.

Since uBLAS equality relies on a fuzz factor (the epsilon
macro), it should not throw when the equality is not
certain (and unfortunately, the order relation on
intervals will make it uncertain). It's why I was
suggesting to switch from abs to norm since interval
computations are not necessary in the equality test. I'm
not sure my explanations are clear.