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/SSecurity.h b/common/rfb/SSecurity.h
index 0280574..8ae7902 100644
--- a/common/rfb/SSecurity.h
+++ b/common/rfb/SSecurity.h
@@ -52,8 +52,9 @@
 
   class SSecurity {
   public:
+    SSecurity(SConnection* sc) { this->sc = sc; }
     virtual ~SSecurity() {}
-    virtual bool processMsg(SConnection* sc)=0;
+    virtual bool processMsg() = 0;
     virtual int getType() const = 0;
 
     // getUserName() gets the name of the user attempting authentication.  The
@@ -63,6 +64,9 @@
     virtual const char* getUserName() const = 0;
 
     virtual SConnection::AccessRights getAccessRights() const { return SConnection::AccessDefault; }
+
+  protected:
+    SConnection* sc;
   };
 
 }