For GLA, @program needs to know that copying is oplus

MWE:

```julia
@present Mat(FreeLinearMaps) begin
X::Ob
Y::Ob
Z::Ob

f::Hom(X,Y)
g::Hom(Y,Z)
h::Hom(Y⊕Z, V)
end

A = @program Mat (x::X,y::Y) begin
v = h(f(x), g(y))
return v
end
```