`table:max-value` and `table:max-key` to get the maximum value and key of the maximum value from a table

[EwoutH]

It would be very useful to have to functions, let's say table:max-value and table:max-key, which giver the maximum value in a table and the key corresponding to that value.

For example, given the following table:

let fruit table:make
table:put fruit "apple" 2
table:put fruit "orange" 5
table:put fruit "banana" 3

table:max-value fruit would give 5, while table:max-key fruit would give "orange".