Add missing <csting> include.

Patch from Cyril Brulebois <cyril.brulebois@enst-bretagne.fr> via
Debian. Closes Debian bug #455304.

examples/cpp/encode/file/main.cpp

@@ -34,6 +34,8 @@
 #include "FLAC++/metadata.h"
 #include "FLAC++/encoder.h"
 
+#include <cstring>
+
 class OurEncoder: public FLAC::Encoder::File {
 public:
 	OurEncoder(): FLAC::Encoder::File() { }