LibVNCClient: don't leak uninitialised memory to remote

The pad fields of the rfbClientCutTextMsg and rfbKeyEventMsg could contain arbitray memory belonging to the process,
don't leak this to the remote.

Closes #252
(cherry picked from commit 2f5b2ad1c6c99b1ac6482c95844a84d66bb52838)

krdc/vnc/rfbproto.c

@@ -501,6 +501,7 @@ SendKeyEvent(CARD32 key, Bool down)
 {
   rfbKeyEventMsg ke;
 
+  memset(&ke, 0, sizeof(ke));
   ke.type = rfbKeyEvent;
   ke.down = down ? 1 : 0;
   ke.key = Swap32IfLE(key);
@@ -518,6 +519,7 @@ SendClientCutText(const char *str, int len)
 {
   rfbClientCutTextMsg cct;
 
+  memset(&cct, 0, sizeof(cct));
   cct.type = rfbClientCutText;
   cct.length = Swap32IfLE((unsigned int)len);
   return  (WriteExact(rfbsock, (char *)&cct, sz_rfbClientCutTextMsg) &&