Fix rotation of falling facedir nodes in some cases

[grorp]

The rotation of falling facedir nodes with param2 values of e.g. 255 and 24-31 is incorrect.

The engine calculates the facedir value by doing param2 % 32 % 24. The falling node code that calculates the facedir value only does param2 % 32 and doesn't rotate nodes where param2 % 32 > 23 at all.

The relevant code in MapNode::getFaceDir:

minetest/src/mapnode.cpp

Line 151 in 2351c95

return (getParam2() & 0x1F) % 24;

and in falling.lua:

minetest/builtin/game/falling.lua

Lines 161 to 166 in 2351c95

	local fdir = node.param2 % 32
	-- Get rotation from a precalculated lookup table
	local euler = facedir_to_euler[fdir + 1]
	if euler then
	self.object:set_rotation(euler)
	end

This PR changes falling.lua to calculate the facedir value in the same way as the engine. It also adds a test node to Devtest, testnodes:falling_facedir.

To do

This PR is Ready for Review.

How to test

In Devtest, place a testnodes:falling_facedir node and set its param2 to 255. See that it is rotated incorrectly while falling without the changes to falling.lua and correctly with them.

[sfan5]

Works.

[SmallJoker]

LGTM