DEP: Deprecate boolean `-` operations

Boolean - is not well defined, especially the unary and
binary operator are not compatible. In general boolean
minus seems to have no real application and does not do
what might be expected.

All "allclose" type functions (numpy, tests, masked) have to
now check for boolean to avoid the deprecation warning. In
the future one could think about removing it again and just
allowing the upcast.
BUG: Force allclose logic to use inexact type

Casting y to an inexact type fixes problems such as
abs(MIN_INT) < 0, and generally makes sense since the allclose
logic is inherently for float types.
Merge pull request #4105 from seberg/deprecate-boolean-math

DEP: Deprecate boolean math operations