Description: Define the support of a function against a "zero" value. According to
Wikipedia ("Support (mathematics)", 31-Mar-2019,
https://en.wikipedia.org/wiki/Support_(mathematics) ) "In mathematics,
the support of a real-valued function f is the subset of the domain
containing those elements which are not mapped to zero." and "The notion
of support also extends in a natural way to functions taking values in
more general sets than R [the real numbers] and to other objects.". The
following definition allows for such extensions, being applicable for
any sets (which usually are functions) and any element (even not
necessarily from the range of the function) regarded as "zero".
(Contributed by AV, 31-Mar-2019)(Revised by AV, 6-Apr-2019)