Call correct wrappers for clipboard handling

We incorrectly called the underlying functions instead of the safe
wrappers for the new clipboard functions. This had the effect of a)
crashing the entire server if one of these functions failed, and b) not
respecting the settings disabling the clipboard.

(cherry picked from commit 331a27addf)

common/rfb/VNCServerST.cxx

@@ -339,7 +339,7 @@ void VNCServerST::requestClipboard()
   if (clipboardClient == NULL)
     return;
 
-  clipboardClient->requestClipboard();
+  clipboardClient->requestClipboardOrClose();
 }
 
 void VNCServerST::announceClipboard(bool available)
@@ -353,7 +353,7 @@ void VNCServerST::announceClipboard(bool available)
 
   for (ci = clients.begin(); ci != clients.end(); ci = ci_next) {
     ci_next = ci; ci_next++;
-    (*ci)->announceClipboard(available);
+    (*ci)->announceClipboardOrClose(available);
   }
 }
 
@@ -367,7 +367,7 @@ void VNCServerST::sendClipboardData(const char* data)
   for (ci = clipboardRequestors.begin();
        ci != clipboardRequestors.end(); ci = ci_next) {
     ci_next = ci; ci_next++;
-    (*ci)->sendClipboardData(data);
+    (*ci)->sendClipboardDataOrClose(data);
   }
 
   clipboardRequestors.clear();