Purge ‘using namespace std’ from header files

std::bind and boost::lambda::bind don’t mix.

Signed-off-by: Anders Kaseorg <andersk@mit.edu>

src/examples/encrypt.cc

@@ -27,6 +27,7 @@
 #include "crypto.h"
 
 using namespace Crypto;
+using namespace std;
 
 int main( int argc, char *argv[] )
 {