expressing the call analysis

[Stephen Weeks]

> The most reasonable solution seems to be to note that N and T are
> multisets, corresponding to the way one would likely process nontail and
> tail calls in an implementation. 

Fine with me.  Another option would be to keep them as sets, but explicitly
include the count in the tuple.  I.E., 
	TailCall = Fun x Fun x Nat
	NonTailCall = Fun x Fun x Jump x Nat

It might be better to go with the counts since people are more familiar with
sets, but either way is fine with me.