Fix compile error with gcc 4.7

lib/engine/account/bank-impl.h

@@ -203,7 +203,7 @@ template<typename AccountType>
 void
 Ekiga::BankImpl<AccountType>::add_account (boost::shared_ptr<AccountType> account)
 {
-  add_object (account);
+  this->add_object (account);
 
   account->questions.connect (boost::ref (questions));
 }
@@ -213,7 +213,7 @@ template<typename AccountType>
 void
 Ekiga::BankImpl<AccountType>::remove_account (boost::shared_ptr<AccountType> account)
 {
-  remove_object (account);
+  this->remove_object (account);
 }
 
 #endif

lib/engine/addressbook/book-impl.h

@@ -204,7 +204,7 @@ void
 Ekiga::BookImpl<ContactType>::add_contact (boost::shared_ptr<ContactType> contact)
 {
   contact->questions.connect (boost::ref (questions));
-  add_object (contact);
+  this->add_object (contact);
 }
 
 
@@ -212,7 +212,7 @@ template<typename ContactType>
 void
 Ekiga::BookImpl<ContactType>::remove_contact (boost::shared_ptr<ContactType> contact)
 {
-  remove_object (contact);
+  this->remove_object (contact);
 }
 
 #endif

lib/engine/addressbook/source-impl.h

@@ -206,7 +206,7 @@ template<typename BookType>
 void
 Ekiga::SourceImpl<BookType>::add_book (boost::shared_ptr<BookType> book)
 {
-  add_object (book);
+  this->add_object (book);
 
   add_connection (book, book->contact_added.connect (boost::bind (boost::ref (contact_added), book, _1)));
 

lib/engine/presence/cluster-impl.h

@@ -147,7 +147,7 @@ Ekiga::ClusterImpl<HeapType>::add_heap (boost::shared_ptr<HeapType> heap)
 
   add_connection (heap, heap->questions.connect (boost::ref (questions)));
 
-  add_object (heap);
+  this->add_object (heap);
 }
 
 template<typename HeapType>

lib/engine/presence/heap-impl.h

@@ -160,14 +160,14 @@ Ekiga::HeapImpl<PresentityType>::add_presentity (boost::shared_ptr<PresentityTyp
 {
   presentity->questions.connect (boost::ref (questions));
 
-  add_object (presentity);
+  this->add_object (presentity);
 }
 
 template<typename PresentityType>
 void
 Ekiga::HeapImpl<PresentityType>::remove_presentity (boost::shared_ptr<PresentityType> presentity)
 {
-  remove_object (presentity);
+  this->remove_object (presentity);
 }
 
 #endif