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/Python/pystrtod.c b/Python/pystrtod.c
index e7bc22c..3f0328e 100644
--- a/Python/pystrtod.c
+++ b/Python/pystrtod.c
@@ -364,7 +364,7 @@
 	/* At this point, p points just past the right-most character we
 	   want to format.  We need to add the grouping string for the
 	   characters between buffer and p. */
-	return _PyBytes_InsertThousandsGrouping(buffer, len, p,
+	return _PyString_InsertThousandsGrouping(buffer, len, p,
 						 buf_size, NULL, 1);
 }