frame f -- provides the frame of values for local variables bound up in a function closure.
It also works when f is a symbol, and returns the frame for the scope it was defined in, even if the function that created it has returned.
The return value is a mutable list, so it's possible to modify the values of the local variables, but it's probably not a good idea.
Exception: if the scope of f is the global scope, then an empty list is returned instead, since some of the global variables are protected.
This function is provisional, and is to be used mainly for debugging.
Class of returned value: MutableList -- the class of all mutable lists