Clean up internal clipboard handling

We now filter incoming data, which means we can start assuming the
clipboard data is always null terminated. This allows us to clean
up a lot of the internal handling.
diff --git a/win/rfb_win32/Clipboard.cxx b/win/rfb_win32/Clipboard.cxx
index fca6c1d..4952695 100644
--- a/win/rfb_win32/Clipboard.cxx
+++ b/win/rfb_win32/Clipboard.cxx
@@ -113,11 +113,11 @@
             // Notify clients
             if (notifier) {
               if (!clipdata) {
-                notifier->notifyClipboardChanged(0, 0);
+                notifier->notifyClipboardChanged(0);
               } else {
                 CharArray unix_text(convertLF(clipdata, strlen(clipdata)));
                 removeNonISOLatin1Chars(unix_text.buf);
-                notifier->notifyClipboardChanged(unix_text.buf, strlen(unix_text.buf));
+                notifier->notifyClipboardChanged(unix_text.buf);
               }
             } else {
               vlog.debug("no clipboard notifier registered");