Upgrade unbound library

These files were pulled from the 1.6.3 release tarball.

This new version builds against OpenSSL version 1.1 which will be
the default in the new Debian Stable which is due to be released
RealSoonNow (tm).

external/unbound/validator/val_secalgo.h

@@ -59,6 +59,14 @@ size_t nsec3_hash_algo_size_supported(int id);
 int secalgo_nsec3_hash(int algo, unsigned char* buf, size_t len,
         unsigned char* res);
 
+/**
+ * Calculate the sha256 hash for the data buffer into the result.
+ * @param buf: buffer to digest.
+ * @param len: length of the buffer to digest.
+ * @param res: result is stored here (space 256/8 bytes).
+ */
+void secalgo_hash_sha256(unsigned char* buf, size_t len, unsigned char* res);
+
 /**
  * Return size of DS digest according to its hash algorithm.
  * @param algo: DS digest algo.