added const in a couple places to make sure the iterator operators

that should be const (like operator* and operator[]) are indeed const


[SVN r8466]

libs/iterator

@@ -1 +1 @@
-Subproject commit e6191bc913a85e0e1a2e1606540f6f52e4d0d485
+Subproject commit 42ddb0d47b32f02e9fd5704c69968bb0544bf022