CSE machine in Scheme: Hide make_number calls

[martin-henz]

Consider the program: (+ 3i 4) Currently we get: I suggest that we change the step sequence by "suppressing" the application of make_number. So (make_number 3i) will just be rendered as 3i in Control, and the next step will have 3i in Stash.

The notion of "suppressing" steps might come in handy elsewhere, too, so it may be a good idea to think about how to do this nicely.