xio with view + newaxis never compiles

[wolfv]

This snippet never finishes compiling for me (no error, just takes forever):

	xt::xarray<double> d1 = xt::random::rand<double>({5});
	auto d12 = view(d1, newaxis(), all());
	std::cout << d12 << std::endl;

However, this compiles fine:

	xt::xarray<double> d1 = xt::random::rand<double>({5});
	auto d12 = view(d1, newaxis(), all());
	xt::xarray<double> a = d12;
	std::cout << a << std::endl;

[wolfv]

Ok, I investigated this a bit more, and the bug is somewhere in either integral_count<S...>() or newaxis_count<S...>() in the const oeprator() accessor in xview. But I am still not sure why it's infinitely recursing (or whatever is exactly happening).

It's happening when using the accessor with empty Args...

[wolfv]

ahhhhhhhhhhhhhhhhhhhhh

std::make_index_sequence<sizeof...(Args)
                                                    + integral_count<S...>()
                                                    - newaxis_count<S...>()

is overflowing if sizeof...(Args) == 0 and newaxis_count<S...>() == 1...