The `arrtoip()` function converts the given byte array into an IP address
string. Array of length 4 are converted to IPv4 addresses, arrays of
length 16 to IPv6 addresses.

Returns the resulting IPv4 or IPv6 address string.

Returns `null` if the given value is not an array, if the array has an
unsuitable length or if any item within the array is not an integer within
the range 0-255.

-- Testcase --
{%
	print(join("\n", [
		arrtoip([ 0, 0, 0, 0 ]),
		arrtoip([ 192, 168, 1, 1 ]),
		arrtoip([ 255, 255, 255, 255 ]),
		arrtoip([ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0 ]),
		arrtoip([ 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 255, 255, 192, 168, 1, 1 ]),
		arrtoip([ 32, 1, 13, 184, 18, 52, 69, 103, 120, 154, 188, 222, 240, 18, 52, 86 ]),
		arrtoip([ 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255, 255 ])
	]), "\n");
%}
-- End --

-- Expect stdout --
0.0.0.0
192.168.1.1
255.255.255.255
::
::ffff:192.168.1.1
2001:db8:1234:4567:789a:bcde:f012:3456
ffff:ffff:ffff:ffff:ffff:ffff:ffff:ffff
-- End --


Supplying a non-array value, an array of unsuitable length or an array
containing invalid byte values yields `null`.

-- Testcase --
{%
	print(join("\n", [
		arrtoip(true),
		arrtoip([ ]),
		arrtoip([ 1, 2, 3 ]),
		arrtoip([ 192, 168, 1, -1 ]),
		arrtoip([ true, false, -5, 500 ])
	]), "\n");
%}
-- End --

-- Expect stdout --
null
null
null
null
null
-- End --