Function: make_map

--Usage--
> make_map(keys: some_list, values: some_list)

Creates a new map. Converts the elements in keys to strings, and uses them as keys for the elements in values.

Produces a warning if keys and values are not of the same size.
nil keys will be ignored.

--Parameters--
! Parameter	Type				Description
| @keys@	[[type:list]]		List of keys.
| @values@	[[type:list]]		List of values.

--Examples--
> make_map(keys:["apple", "durian", 3], values:["good", "bad", "not edible"]) == ["apple":"good", "durian":"bad", "3":"not edible"]