Add message_is_sent_by_us stub

tests/unittests/xmpp/stub_xmpp.c

@@ -3,6 +3,7 @@
 #include <setjmp.h>
 #include <cmocka.h>
 
+#include "xmpp/message.h"
 #include "xmpp/xmpp.h"
 
 // connection functions
@@ -132,6 +133,10 @@ void message_send_gone(const char * const barejid) {}
 void message_send_invite(const char * const room, const char * const contact,
     const char * const reason) {}
 
+bool message_is_sent_by_us(ProfMessage *message) {
+    return TRUE;
+}
+
 // presence functions
 void presence_subscription(const char * const jid, const jabber_subscr_t action) {}