SF bug #477221: abs and divmod act oddly with -0.0.

Partial fix.
float_abs():  ensure abs(-0.0) returns +0.0.
Bugfix candidate.

Objects/floatobject.c

@@ -570,8 +570,10 @@ float_abs(PyFloatObject *v)
 {
 	if (v->ob_fval < 0)
 		return float_neg(v);
-	else
+	else if (v->ob_fval > 0)
 		return float_pos(v);
+	else /* ensure abs(-0) is +0 */
+		return PyFloat_FromDouble(+0.0);
 }
 
 static int