Fix brown paper bag bug in 5c47c6546c.

The previous logic failed to work for anything other than the first
segment of a relation.

Report by Jakub Wartak. Patch by me.

Discussion: http://postgr.es/m/CAKZiRmwd3KTNMQhm9Bv4oR_1uMehXroO6kGyJQkiw9DfM8cMwQ@mail.gmail.com

src/backend/storage/file/reinit.c

@@ -431,7 +431,7 @@ parse_filename_for_nontemp_relation(const char *name, RelFileNumber *relnumber,
 	else
 	{
 		/* Reject leading zeroes, just like we do for RelFileNumber. */
-		if (name[0] < '1' || name[0] > '9')
+		if (name[1] < '1' || name[1] > '9')
 			return false;
 
 		errno = 0;