Remove destroy functions

These are just confusing and obfuscating. Do a normal delete of
these objects instead.
diff --git a/common/rfb/CConnection.cxx b/common/rfb/CConnection.cxx
index ce489b1..d7a9d85 100644
--- a/common/rfb/CConnection.cxx
+++ b/common/rfb/CConnection.cxx
@@ -49,7 +49,8 @@
 CConnection::~CConnection()
 {
   setFramebuffer(NULL);
-  if (csecurity) csecurity->destroy();
+  if (csecurity)
+    delete csecurity;
   delete reader_;
   reader_ = 0;
   delete writer_;