Refactor some longobject internals: PyLong_AsDouble and _PyLong_AsScaledDouble
(the latter renamed to _PyLong_Frexp) now use the same core code. The
exponent produced by _PyLong_Frexp now has type Py_ssize_t instead of the
previously used int, and no longer needs scaling by PyLong_SHIFT. This
frees the math module from having to know anything about the PyLong
implementation. This closes issue #5576.
git-svn-id: http://svn.python.org/projects/python/trunk@77234 6015fed2-1504-0410-9fe1-9d1591cc4771