Back out "Patch #1643874: memory leak in ctypes fixed."

The code in this patch leaves no way to give up the ownership of a
BSTR instance.

Misc/NEWS

@@ -361,8 +361,6 @@ Library
 
 - Bug #1643943: Fix time.strptime's support for the %U directive.
 
-- Patch #1643874: memory leak in ctypes fixed.
-
 - Patch #1507247: tarfile.py: use current umask for intermediate
   directories.
 

Modules/_ctypes/cfield.c

@@ -1461,19 +1461,10 @@ Z_get(void *ptr, unsigned size)
 #endif
 
 #ifdef MS_WIN32
-/* We cannot use SysFreeString as the PyCObject_FromVoidPtr
-   because of different calling convention
-*/
-static void _my_SysFreeString(void *p)
-{
-	SysFreeString((BSTR)p);
-}
-
 static PyObject *
 BSTR_set(void *ptr, PyObject *value, unsigned size)
 {
 	BSTR bstr;
-	PyObject *result;
 
 	/* convert value into a PyUnicodeObject or NULL */
 	if (Py_None == value) {
@@ -1501,19 +1492,15 @@ BSTR_set(void *ptr, PyObject *value, unsigned size)
 	} else
 		bstr = NULL;
 
-	if (bstr) {
-		result = PyCObject_FromVoidPtr((void *)bstr, _my_SysFreeString);
-		if (result == NULL) {
-			SysFreeString(bstr);
-			return NULL;
-		}
-	} else {
-		result = Py_None;
-		Py_INCREF(result);
-	}
-
+	/* free the previous contents, if any */
+	if (*(BSTR *)ptr)
+		SysFreeString(*(BSTR *)ptr);
+	
+	/* and store it */
 	*(BSTR *)ptr = bstr;
-	return result;
+
+	/* We don't need to keep any other object */
+	_RET(value);
 }