Here's stage 2:  remove uses of tp_compare from Objects and Modules, and
replace uses of PyObject_Compare with PyObject_RichCompareBool.
PyObject_Compare, cmp and friends still haven't been removed at this
stage.

In detail:
  - for cell objects, method wrapper objects, PyTclObjects, and
    PyST_Objects (in the parser module), remove the defined tp_compare
    methods and implement tp_richcompare instead.
  - add tests for cell comparisons and PyST_Object comparisons;  
reenable
    tests for method wrapper comparisons.  There are no tests for the
    PyTclObject comparisons.
  - remove tp_compare method from sets (all it did was emit an error
    message about the nonsensicality of doing order comparisons on sets)
  - in Objects/rangeobject.c and ElementTree, replace uses of
    PyObject_Compare with PyObject_RichCompareBool