Use the new Unicode API

 * Replace PyUnicode_FromUnicode(NULL, 0) by PyUnicode_New(0, 0)
 * Replce PyUnicode_FromUnicode(str, len) by PyUnicode_FromWideChar(str, len)
 * Replace Py_UNICODE by wchar_t
 * posix_putenv() uses PyUnicode_FromFormat() to create the string, instead
   of PyUnicode_FromUnicode() + _snwprintf()
diff --git a/Python/dynload_win.c b/Python/dynload_win.c
index e511098..2cbfe9f 100644
--- a/Python/dynload_win.c
+++ b/Python/dynload_win.c
@@ -249,7 +249,7 @@
                     "DLL load failed: ");
 
                 PyUnicode_AppendAndDel(&message,
-                    PyUnicode_FromUnicode(
+                    PyUnicode_FromWideChar(
                         theInfo,
                         theLength));
             }