Correct frexp() docs for non-finite numbers

Doc/library/math.rst

@@ -255,10 +255,11 @@ Floating point manipulation functions
 
 .. function:: frexp(x)
 
-   Return the mantissa and exponent of *x* as the pair ``(m, e)``.  *m* is a float
-   and *e* is an integer such that ``x == m * 2**e`` exactly. If *x* is zero,
-   returns ``(0.0, 0)``, otherwise ``0.5 <= abs(m) < 1``.  This is used to "pick
-   apart" the internal representation of a float in a portable way.
+   Return the mantissa and exponent of *x* as the pair ``(m, e)``.  *m* is a
+   float and *e* is an integer such that ``x == m * 2**e`` exactly.  If *x*
+   is a finite nonzero number, then ``0.5 <= abs(m) < 1.0``.  Else, returns
+   ``(x, 0)``.  This is used to "pick apart" the internal representation of
+   a float in a portable way.
 
    Note that :func:`frexp` has a different call/return pattern
    than its C equivalents: it takes a single argument and return a pair of

Modules/mathmodule.c

@@ -1439,12 +1439,13 @@ math.frexp
 Return the mantissa and exponent of x, as pair (m, e).
 
 m is a float and e is an int, such that x = m * 2.**e.
-If x is 0, m and e are both 0.  Else 0.5 <= abs(m) < 1.0.
+If x is a finite nonzero number, then 0.5 <= abs(m) < 1.0.
+Else, e is zero and m is x.
 [clinic start generated code]*/
 
 static PyObject *
 math_frexp_impl(PyObject *module, double x)
-/*[clinic end generated code: output=03e30d252a15ad4a input=96251c9e208bc6e9]*/
+/*[clinic end generated code: output=03e30d252a15ad4a input=49202d05c5d2c699]*/
 {
     int i;
     /* deal with special cases directly, to sidestep platform