Fix missing 'typename' prior to dependent type name error

On Ubuntu 17.10 with gcc 7.2 or clang 3.9,
compiler threw the error when trying to
use the append(Iterator) method on a name

Change-Id: I5252280cfc9021d81d6bb996012255e226006a45
diff --git a/src/name.hpp b/src/name.hpp
index a2efe1b..b27f3fd 100644
--- a/src/name.hpp
+++ b/src/name.hpp
@@ -293,7 +293,7 @@
   Name&
   append(Iterator first, Iterator last)
   {
-    static_assert(sizeof(std::iterator_traits<Iterator>::value_type) == 1,
+    static_assert(sizeof(typename std::iterator_traits<Iterator>::value_type) == 1,
                   "iterator does not dereference to one-octet value type");
     return append(Component(first, last));
   }