Remove MSVC exclusions from AnyStruct::Reader and OwnOwn

c++/src/capnp/any.h

@@ -452,11 +452,9 @@ public:
   Reader() = default;
   inline Reader(_::StructReader reader): _reader(reader) {}
 
-#if !_MSC_VER  // TODO(msvc): MSVC ICEs on this. Try restoring when compiler improves.
   template <typename T, typename = kj::EnableIf<CAPNP_KIND(FromReader<T>) == Kind::STRUCT>>
   inline Reader(T&& value)
       : _reader(_::PointerHelpers<FromReader<T>>::getInternalReader(kj::fwd<T>(value))) {}
-#endif
 
   kj::ArrayPtr<const byte> getDataSection() {
     return _reader.getDataSectionAsBlob();

c++/src/kj/memory.h

@@ -208,15 +208,10 @@ class OwnOwn {
 public:
   inline OwnOwn(Own<T>&& value) noexcept: value(kj::mv(value)) {}
 
-#if _MSC_VER
-  inline Own<T>& operator*() { return value; }
-  inline const Own<T>& operator*() const { return value; }
-#else
   inline Own<T>& operator*() & { return value; }
   inline const Own<T>& operator*() const & { return value; }
   inline Own<T>&& operator*() && { return kj::mv(value); }
   inline const Own<T>&& operator*() const && { return kj::mv(value); }
-#endif
   inline Own<T>* operator->() { return &value; }
   inline const Own<T>* operator->() const { return &value; }
   inline operator Own<T>*() { return value ? &value : nullptr; }