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.

src/z85util.h

@@ -1,7 +1,9 @@
 #ifndef _HAVE_PCP_Z85
 #define _HAVE_PCP_Z85
 
+#ifndef _BSD_SOURCE
 #define _BSD_SOURCE
+#endif
 
 #include <unistd.h>
 #include <stdio.h>