Adjust tests so that pretty printing reference also works on Windows.
Global variable to define the behavior of prettystr for printing table refs
- dedicated test for prettystr with ref-printing on
- all tests are back to their previous syntax, without ref-printing
- improvement to test setUp(): restore global variables to their previous value
  instead of a hardcoded value
Force printing of table-refs in error messages when table recursion is detected.

- fix one place where the old syntax for printing ref was still in use
- create a sub-function prettystr_sub for dealing with recursion
- use a two-pass approach to force table-refs when recursion is detected
- add two test-cases for untested code paths