Support extended clipboard transfers

Implements support in both client and server for the extended
clipboard format first seen in UltraVNC. Currently only implements
text handling, but that is still an improvement as it extends the
clipboard from ISO 8859-1 to full Unicode.
diff --git a/common/rfb/ClientParams.h b/common/rfb/ClientParams.h
index f7a7044..aab3d64 100644
--- a/common/rfb/ClientParams.h
+++ b/common/rfb/ClientParams.h
@@ -1,5 +1,5 @@
 /* Copyright (C) 2002-2005 RealVNC Ltd.  All Rights Reserved.
- * Copyright 2014-2018 Pierre Ossman for Cendio AB
+ * Copyright 2014-2019 Pierre Ossman for Cendio AB
  * 
  * This is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -84,6 +84,9 @@
     unsigned int ledState() { return ledState_; }
     void setLEDState(unsigned int state);
 
+    rdr::U32 clipboardFlags() const { return clipFlags; }
+    void setClipboardCaps(rdr::U32 flags, const rdr::U32* lengths);
+
     // Wrappers to check for functionality rather than specific
     // encodings
     bool supportsLocalCursor() const;
@@ -108,6 +111,8 @@
     Cursor* cursor_;
     std::set<rdr::S32> encodings_;
     unsigned int ledState_;
+    rdr::U32 clipFlags;
+    rdr::U32 clipSizes[16];
   };
 }
 #endif