Use iter2--pp-to-string for all tracing output

[telotortium]

Make the output of this much easier to read for complex functions.

See #3

[doublep]

General idea is fine, but parameter indent-by of iter2--pp-to-string is used to indent subsequent lines so that they align nicely with the first line. E.g. in (format "FORM: %s" (iter2--pp-to-string form 60 6)) number 6 is the length of string "FORM: ". So, in places where you add calls to the function 6 is likely not correct.

Also, you'd need to make sure that the tests pass. If needed, you can adjust the tests rather than the code, they are supposed to assert expected output, not be fixed in stone.