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/unix/x0vncserver/XDesktop.cxx b/unix/x0vncserver/XDesktop.cxx
index 564b2d5..8be9aa3 100644
--- a/unix/x0vncserver/XDesktop.cxx
+++ b/unix/x0vncserver/XDesktop.cxx
@@ -406,7 +406,7 @@
 #endif
 }
 
-void XDesktop::clientCutText(const char* str, int len) {
+void XDesktop::clientCutText(const char* str) {
 }
 
 ScreenSet XDesktop::computeScreenLayout()