Remove destroy functions

These are just confusing and obfuscating. Do a normal delete of
these objects instead.
diff --git a/common/rfb/SConnection.cxx b/common/rfb/SConnection.cxx
index 6b81055..ae43254 100644
--- a/common/rfb/SConnection.cxx
+++ b/common/rfb/SConnection.cxx
@@ -64,7 +64,8 @@
 
 SConnection::~SConnection()
 {
-  if (ssecurity) ssecurity->destroy();
+  if (ssecurity)
+    delete ssecurity;
   delete reader_;
   reader_ = 0;
   delete writer_;