util.startup: Check root after detecting platform and reading config (thanks SigmaTel71) Ensures that startup.detect_platform() runs so know whether to use the POSIX method of checking the current user or something else. Also after reading the config so we know whether the root override setting is set.

local xpcall = xpcall;

if select(2, xpcall(function (x) return x end, function () end,  "test")) ~= "test" then
	xpcall = require"prosody.util.compat".xpcall;
end

return {
	xpcall = xpcall;
};