Missing Base.deepcopy_internal for Group interface

[thofma]

Was doing some computations and encountered:

ERROR: Missing method from Group interface: `Base.deepcopy_internal(::PcGroupElem, ::IdDict)`
Stacktrace:
[...]

[fingolfin]

Related: oscar-system/GAP.jl#197

[ThomasBreuer]

How to reproduce the problem:
deepcopy([one(small_group(2, 1))])

[fingolfin]

Full backtrace:

julia> deepcopy([one(small_group(2, 1))])
ERROR: Missing method from Group interface: `Base.deepcopy_internal(::PcGroupElem, ::IdDict)`
Stacktrace:
 [1] deepcopy_internal(g::PcGroupElem, stackdict::IdDict{Any, Any})
   @ GroupsCore ~/.julia/packages/GroupsCore/63Vm8/src/group_elements.jl:30
 [2] _deepcopy_array_t(x::Array, T::Type, stackdict::IdDict{Any, Any})
   @ Base ./deepcopy.jl:105
 [3] deepcopy_internal
   @ ./deepcopy.jl:92 [inlined]
 [4] deepcopy(x::Vector{PcGroupElem})
   @ Base ./deepcopy.jl:26
 [5] top-level scope
   @ REPL[2]:1

So GroupsCore forces us to be nice and implement the interface properly :-). OK, so we just have to do that. @ThomasBreuer will work on it.

[fingolfin]

Resolved by #1037