Fix cloud fog being broken for high clouds (maybe)

[Wuzzy2]

This PR might fix #8340.

But this is just a quick and dirty bugfix attempt, I made only superficial testing, which worked. But I have no idea if this bugfix is really fixing cloud fog for good or if this is only a fake fix.

So please check for yourself, if it makes sense.

[sfan5]

m_box has the camera offset subtracted:

minetest/src/client/clouds.h

Lines 125 to 126 in f0725ce

	m_box = aabb3f(-BS * 1000000.0f, height_bs - BS * m_camera_offset.Y, -BS * 1000000.0f,
	BS * 1000000.0f, height_bs + thickness_bs - BS * m_camera_offset.Y, BS * 1000000.0f);

Camera::update() is called with camera offset added:

minetest/src/client/game.cpp

Lines 3752 to 3758 in f0725ce

	v3f camera_node_position = camera->getCameraNode()->getPosition();
	v3s16 camera_offset = camera->getOffset();
	camera_node_position.X = camera_node_position.X + camera_offset.X * BS;
	camera_node_position.Y = camera_node_position.Y + camera_offset.Y * BS;
	camera_node_position.Z = camera_node_position.Z + camera_offset.Z * BS;
	clouds->update(camera_node_position,
	sky->getCloudColor());

Consequently, height calcuations need to take the camera offset into account.

[Wuzzy2]

Heh, that was exactly my thought process as well. But I just wanted someone to look at it, just in case I overlooked something. :-)