Owl_base_mathsMaths: fundamental and advanced mathematical functions.
``is_inf x`` returns ``true`` if ``x`` is ``infinity`` or ``neg_infinity``.
``is_pow2 x`` return ``true`` if ``x`` is integer power of 2, e.g. 32, 64, etc.
``same_sign x y`` returns ``true`` if ``x`` and ``y`` have the same sign, otherwise it returns ``false``. Positive and negative zeros are special cases and always returns ``true``.