Workaround for gcc limitation (#319)

src/ngraph/ops/constant.cpp

@@ -119,11 +119,22 @@ std::vector<std::string> op::Constant::get_value_strings() const
     return rc;
 }
 
-template <>
-void op::Constant::write_to_buffer<std::string>(const element::Type& target_type,
+//
+// We have to open up namespace blocks here to work around a problem with gcc:
+//
+// https://stackoverflow.com/questions/25594644/warning-specialization-of-template-in-different-namespace
+//
+namespace ngraph
+{
+    namespace op
+    {
+        template <>
+        void Constant::write_to_buffer<std::string>(const element::Type& target_type,
                                                     const Shape& target_shape,
                                                     const std::vector<std::string>& source,
                                                     void* target,
                                                     size_t target_element_count)
-{
+        {
+        }
+    }
 }