This reverts r63675 based on the discussion in this thread:

 http://mail.python.org/pipermail/python-dev/2008-June/079988.html

Python 2.6 should stick with PyString_* in its codebase.  The PyBytes_* names
in the spirit of 3.0 are available via a #define only.  See the email thread.
diff --git a/Modules/main.c b/Modules/main.c
index c1c4b45..895a64f 100644
--- a/Modules/main.c
+++ b/Modules/main.c
@@ -196,7 +196,7 @@
 {
 	PyObject *argv0 = NULL, *importer = NULL;
 
-	if ((argv0 = PyBytes_FromString(filename)) && 
+	if ((argv0 = PyString_FromString(filename)) && 
 	    (importer = PyImport_GetImporter(argv0)) &&
 	    (importer->ob_type != &PyNullImporter_Type))
 	{