mod_smacks: Remove extra optional from sm element Since XEP-0198 version 1.6.3, the optional and required children of sm in stream:features have been removed entirely. They already weren’t specified before, and were only leftover from a very old version in the XML Schema. Fixes #1963

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;
};