_PyImport_FixupExtension() and _PyImport_FindExtension() uses FS encoding

 * Rename _PyImport_FindExtension() to _PyImport_FindExtensionUnicode():
   the filename becomes a Unicode object instead of byte string
 * Rename _PyImport_FixupExtension() to _PyImport_FixupExtensionUnicode():
   the filename becomes a Unicode object instead of byte string
diff --git a/Modules/signalmodule.c b/Modules/signalmodule.c
index d34e177..4691285 100644
--- a/Modules/signalmodule.c
+++ b/Modules/signalmodule.c
@@ -951,7 +951,7 @@
 {
     PyObject *m = PyInit_signal();
     if (m) {
-        _PyImport_FixupExtension(m, "signal", "signal");
+        _PyImport_FixupBuiltin(m, "signal");
         Py_DECREF(m);
     }
 }