binary-xml-wire-format: Partial enabling of binary-xml-wire-format

Due to significant changes, Data abstraction conversion (from and to
wire format) is currently disabled, using empty placeholders instead.

Other data structures should have working conversion (minus
PublisherPublicKeyDigest, which is not part of Interest and
ForwardingEntry data structure anymore).

Change-Id: I51c47495808c35b500fc6b1fcc0c46db217e6598
diff --git a/include/ndn-cpp/exclude.hpp b/include/ndn-cpp/exclude.hpp
index 276aa5b..e26ec31 100644
--- a/include/ndn-cpp/exclude.hpp
+++ b/include/ndn-cpp/exclude.hpp
@@ -95,6 +95,12 @@
    */
   inline bool
   empty () const;
+
+  /**
+   * @brief Clear the exclude filter
+   */
+  inline void
+  clear();
   
   /**
    * @brief Get number of exclude terms
@@ -177,6 +183,13 @@
   return m_exclude.empty ();
 }
 
+inline void
+Exclude::clear ()
+{
+  m_exclude.clear ();
+}
+
+
 inline size_t
 Exclude::size () const
 {
diff --git a/include/ndn-cpp/interest.hpp b/include/ndn-cpp/interest.hpp
index e55a554..8fe3119 100644
--- a/include/ndn-cpp/interest.hpp
+++ b/include/ndn-cpp/interest.hpp
@@ -136,8 +136,10 @@
    * @brief Get Interest's nonce
    *
    * If nonce was not set before this call, it will be automatically assigned to a random value
+   *
+   * Const reference needed for C decoding
    */
-  uint32_t
+  const uint32_t&
   getNonce() const;
     
   void