Return the variable at the end of OBJECT's variable chain.
If OBJECT is a symbol, follow its variable indirections (if any), and
return the variable at the end of the chain of aliases. See Info node
`(elisp)Variable Aliases'.
If OBJECT is not a symbol, just return it. If there is a loop in the
chain of aliases, signal a `cyclic-variable-indirection' error.
(fn OBJECT)