applied patch from Olli Savia for LynxOS Daniel

* libxml.h triodef.h: applied patch from Olli Savia for LynxOS
Daniel

libxml.h

@@ -25,6 +25,13 @@
 #include <libxml/xmlversion.h>
 #endif
 
+#if defined(__Lynx__)
+#include <stdio.h> /* pull definition of size_t */
+#include <varargs.h>
+int snprintf(char *, size_t, const char *, ...);
+int vfprintf(FILE *, const char *, va_list);
+#endif
+
 #ifndef WITH_TRIO
 #include <stdio.h>
 #else