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/CConnection.cxx b/common/rfb/CConnection.cxx
index d7a9d85..fb95377 100644
--- a/common/rfb/CConnection.cxx
+++ b/common/rfb/CConnection.cxx
@@ -235,14 +235,14 @@
   }
 
   state_ = RFBSTATE_SECURITY;
-  csecurity = security.GetCSecurity(secType);
+  csecurity = security.GetCSecurity(this, secType);
   processSecurityMsg();
 }
 
 void CConnection::processSecurityMsg()
 {
   vlog.debug("processing security message");
-  if (csecurity->processMsg(this)) {
+  if (csecurity->processMsg()) {
     state_ = RFBSTATE_SECURITY_RESULT;
     processSecurityResultMsg();
   }