Change gcguard key type

Author: mrkn

RbCall.jl/src/gc.jl

@@ -1 +1 @@
-const gcguard = Dict{RubyObject, Any}()
+const gcguard = Dict{RbPtr, Any}()

RbCall.jl/src/jlwrap.jl

@@ -28,7 +28,7 @@ end
 function jlwrap_new(x::Any)::RubyObject
  obj = TypedData_Make_Struct(cJuliaWrapper, jlwrap_t, jlwrap_data_type)
  Base.unsafe_store!(Ptr{jlwrap_t}(RTYPEDDATA_DATA(obj)), jlwrap_t(obj, x))
- gcguard[obj] = x
+ gcguard[RbPtr(obj)] = x
  return obj
 end