Avoid XKeysymToString() conflict with libX11

We implement our own version of this, and because of this we carry our
lookup table generated by the same tool that libX11 uses. Unfortunately,
that table is a global symbol and as such there might be a mismatch of
which table should be used.

Make sure we get our own copy by changing the name of it. We use a
define rather than modifying ks_tables.h as that file is automatically
generated.

common/rfb/KeysymStr.c

@@ -34,6 +34,9 @@ in this Software without prior written authorization from The Open Group.
 #include "keysymdef.h"
 #include "KeysymStr.h"
 
+/* Change the name of this to avoid conflict with libX11 */
+#define _XkeyTable _vncXkeyTable
+
 #define NEEDKTABLE
 #define NEEDVTABLE
 #include "ks_tables.h"