Make _PyTime_RoundHalfEven() private again

Include/pytime.h

@@ -44,11 +44,6 @@ PyAPI_FUNC(PyObject *) _PyLong_FromTime_t(
 PyAPI_FUNC(time_t) _PyLong_AsTime_t(
     PyObject *obj);
 
-/* Round to nearest with ties going to nearest even integer
-   (_PyTime_ROUND_HALF_EVEN) */
-PyAPI_FUNC(double) _PyTime_RoundHalfEven(
-    double x);
-
 /* Convert a number of seconds, int or float, to time_t. */
 PyAPI_FUNC(int) _PyTime_ObjectToTime_t(
     PyObject *obj,

Python/pytime.c

@@ -60,7 +60,9 @@ _PyLong_FromTime_t(time_t t)
 #endif
 }
 
-double
+/* Round to nearest with ties going to nearest even integer
+   (_PyTime_ROUND_HALF_EVEN) */
+static double
 _PyTime_RoundHalfEven(double x)
 {
     double rounded = round(x);