Fix issues with keyed hash API.

src/libcryptobox/blake2/blake2.c

 blake2b_keyed_init (blake2b_state *S, const unsigned char *key, size_t keylen)
 {
 	unsigned char k[BLAKE2B_BLOCKBYTES] = {0};
-	if (keylen > BLAKE2B_KEYBYTES) {
-		fprintf (stderr,
-				"key size larger than %u passed to blake2b_keyed_init",
-				BLAKE2B_KEYBYTES);
-		exit (-1);
-	}
-	else {
-		memcpy (k, key, keylen);
-	}
+
+	g_assert (keylen <= BLAKE2B_KEYBYTES);
+	memcpy (k, key, keylen);
 	blake2b_init (S);
 	blake2b_update (S, k, BLAKE2B_BLOCKBYTES);
 }
 			}
 		}
 	}
-}
+}

src/libcryptobox/blake2/blake2.h

 		const unsigned char *key,
 		size_t keylen);
 
-int blake2b_load (void);
+void blake2b_load (void);
 
 #if defined(__cplusplus)
 }

src/libcryptobox/cryptobox.h

 #define rspamd_cryptobox_MAX_NMBYTES 32
 #define rspamd_cryptobox_SIPKEYBYTES 16
 #define rspamd_cryptobox_HASHBYTES 64
+#define rspamd_cryptobox_HASHKEYBYTES 64
 #define rspamd_cryptobox_HASHSTATEBYTES 256
 
 typedef guchar rspamd_pk_t[rspamd_cryptobox_MAX_PKBYTES];