Py_CLEAR assigns its argument to a PyObject pointer without
a cast. This causes a warning if the argument is PyObject-
compatible but not actually a PyObject. The other reference
counting macros accept non-PyObjects without a cast by the
user, so Py_CLEAR should too.

The patch is hard to read since it realigns the backslashes
on the macro. diff -b (ignore whitespace) is good in these
cases.