Strongly bind security objects to connection object

There is already an implicit connection between them, so let's make
it explicit. This allows easy lookup outside of the processMsg() function.
diff --git a/common/rfb/CSecurityStack.h b/common/rfb/CSecurityStack.h
index a16003f..4be507e 100644
--- a/common/rfb/CSecurityStack.h
+++ b/common/rfb/CSecurityStack.h
@@ -27,9 +27,10 @@
 
   class CSecurityStack : public CSecurity {
   public:
-    CSecurityStack(int Type, const char *Name, CSecurity* s0 = 0, CSecurity* s1 = 0);
+    CSecurityStack(CConnection* cc, int Type, const char *Name,
+                   CSecurity* s0 = NULL, CSecurity* s1 = NULL);
     ~CSecurityStack();
-    virtual bool processMsg(CConnection* cc);
+    virtual bool processMsg();
     virtual int getType() const {return type;};
     virtual const char* description() const {return name;}
     virtual bool isSecure() const;