Defining `==` for `ComposedFunction` by comparing `inner` and `outer`

[sunxd3]

== for ComposedFunction falls back to egal, c.f.

julia/base/Base.jl

Line 165 in bd47eca

==(x, y) = x === y

Does it make sense to define something like

function Base.:(==)(cf1::ComposedFunction, cf2::ComposedFunction)
    cf1.inner == cf1.inner && cf2.outer== cf2.outer
end

related PR for Accessors.jl: JuliaObjects/Accessors.jl#146

[nsajko]

I suppose the proposal would be easier to evaluate with a PR that passes the test suite.

NB: if you define ==(::T, ::T), it's required to also define hash(::T, ::UInt)