Implemented NetDll_shutdown.

De-borked LoadFdset/StoreFdset in regards to handling of correct counts
and invalid sockets.

src/xenia/kernel/util/shim_utils.h

@@ -317,6 +317,7 @@ using lpunknown_t = const shim::PointerParam&;
 template <typename T>
 using pointer_t = const shim::TypedPointerParam<T>&;
 
+using int_result_t = shim::Result<int32_t>;
 using dword_result_t = shim::Result<uint32_t>;
 using pointer_result_t = shim::Result<uint32_t>;