Change %c format specifier for PyArg_ParseTuple() so that it accepts
a unicode character (an int * must be passed as the argument).

Change %c format specifier for Py_BuildValue() so that it outputs
a unicode object.

Fix datetime.datetime.isoformat(), so that it works if sep is
a unicode character > U+00FF.
diff --git a/Modules/datetimemodule.c b/Modules/datetimemodule.c
index d39791a..488d062 100644
--- a/Modules/datetimemodule.c
+++ b/Modules/datetimemodule.c
@@ -4027,7 +4027,7 @@
 static PyObject *
 datetime_isoformat(PyDateTime_DateTime *self, PyObject *args, PyObject *kw)
 {
-	char sep = 'T';
+	int sep = 'T';
 	static char *keywords[] = {"sep", NULL};
 	char buffer[100];
 	PyObject *result;