fixed libtools portability bug, fixed arc4random() portability,

fixed htobe32 and be32toh portability, fixed error handling in main(),
fixed invalid type parameter for randomart image in pcppubkey_printshortinfo(),
fixed configure search for libsodium.

libpcp/mem.h

@@ -5,6 +5,7 @@
 #include <stdlib.h>
 #include <errno.h>
 #include <err.h>
+#include "platform.h"
 
 // simple malloc()  wrapper 
 // behaves like calloc(), which