Update compat.lua

[EPuncker]

Pull Request Prelude

• I have followed proper The Forgotten Server code styling.
• I have read and understood the contribution guidelines before making this PR.
• I am aware that this PR may be closed if the above-mentioned criteria are not fulfilled.

Changes Proposed

Added two functions to compat.lua that were deprecated or had its name changed in Lua 5.2

Issues addressed:
closes #4109

[Zbizu]

works, demo to test:

https://www.lua.org/cgi-bin/demo

t = {
[1] = 30,
["abc"] = 70,
[14] = 100,
["def"] = 10000
}

function table.maxn(t)
	local max = 0
	for k in pairs(t) do
		if type(k) == "number" and k > max then
			max = k
		end
	end
	return max
end

print(table.maxn(t))

[ranisalt]

Doesn't Lua publish some global compatibility code? Since they make so many breaking changes from one version to the other, I feel like the language developers should provide that path

[EPuncker]

Doesn't Lua publish some global compatibility code? Since they make so many breaking changes from one version to the other, I feel like the language developers should provide that path

there is this: http://lua-users.org/wiki/LuaVersionCompatibility but I don't know