Remove defintion of iszero

Was added in #305.

README.md

@@ -136,8 +136,6 @@ Currently, the `@compat` macro supports the following syntaxes:
 
 * `>:`, a supertype operator for symmetry with `issubtype` (`A >: B` is equivalent to `B <: A`), can be used in 0.5 and earlier ([#20407]).
 
-* `iszero(x)` efficiently checks whether `x == zero(x)` (including arrays) can be used in 0.5 and earlier ([#19950]).
-
 * `.&` and `.|` are short syntax for `broadcast(&, xs...)` and `broadcast(|, xs...)` (respectively) in Julia 0.6 (only supported on Julia 0.5 and above) ([#17623])
 
 * `Compat.isapprox` with `nans` keyword argument ([#20022])
@@ -492,7 +490,6 @@ includes this fix. Find the minimum version from there.
 [#19449]: https://github.com/JuliaLang/julia/issues/19449
 [#19635]: https://github.com/JuliaLang/julia/issues/19635
 [#19784]: https://github.com/JuliaLang/julia/issues/19784
-[#19950]: https://github.com/JuliaLang/julia/issues/19950
 [#20005]: https://github.com/JuliaLang/julia/issues/20005
 [#20022]: https://github.com/JuliaLang/julia/issues/20022
 [#20164]: https://github.com/JuliaLang/julia/issues/20164

src/Compat.jl

@@ -142,15 +142,6 @@ else
     end
 end
 
-# julia #19950
-@static if !isdefined(Base, :iszero)
-    # 0.6
-    iszero(x) = x == zero(x)
-    iszero(x::Number) = x == 0
-    iszero(x::AbstractArray) = all(iszero, x)
-    export iszero
-end
-
 # julia　#20407
 @static if !isdefined(Base, :(>:))
     # 0.6

test/runtests.jl

@@ -62,22 +62,6 @@ let s = "Koala test: 🐨"
     end
 end
 
-# julia#19950, tests from Base (#20028)
-for T in (Float16, Float32, Float64, BigFloat, Int8, Int16, Int32, Int64, Int128,
-          BigInt, UInt8, UInt16, UInt32, UInt64, UInt128)
-    @test iszero(T(0))
-    @test iszero(Complex{T}(0))
-    if T<:Integer
-        @test iszero(Rational{T}(0))
-    end
-    if T<:AbstractFloat
-        @test iszero(T(-0.0))
-        @test iszero(Complex{T}(-0.0))
-    end
-end
-@test !iszero([0, 1, 2, 3])
-@test iszero([0, 0, 0, 0])
-
 let
     x = view(1:10, 2:4)
     D = Diagonal(x)