`Base.iszero` not fully compatible using `IntervalArithmetic` values

In their 1.0 update, the design of `IntervalArithmetic` changed so that `Base.iszero` will throw this error when value is an interval overlapping zero: ```julia > iszero(interval(-1, 1)) ERROR: ArgumentError: `==` is purposely not supported for overlapping non-thin intervals. See instead `isequal_interval` ``` A solution using `isthinzero` is thus suggested, which outputs `false` only if the compared value is a thin zero (no other floating-point values in the interval). ```julia > isthinzero(interval(-0,0)) ## true > isthinzero(interval(-0.0,0.0)) ## true > isthinzero(interval(prevfloat(-0.0),0.0)) ## false > isthinzero(interval(0.0,nextfloat(0.0))) ## false ``` Please consider updating compatibility with `IntervalArithmetic` again, thank you. Note, that an `Interval` is a `Real` type, so it matches the second of the following rules (`::Number`) in your internal `_iszero` method: ```julia @inline _iszero(x) = iszero(x) === true @inline _iszero(x::Number) = iszero(x) @inline _iszero(x::AbstractArray) = iszero(x) ```