hash/tiger: use read_array to avoid alignment issues

hash/tiger.cpp

@@ -347,14 +347,9 @@ tiger::operator() (cruft::view<u08 const *> data) noexcept
         while (bytes.size () >= 64) {
             auto [head08, tail] = bytes.split (8 * 8);
             bytes = tail;
-            auto head64 = head08.cast<u64 const*> ();
 
             std::array<u64,8> x;
-            std::copy (
-                std::begin (head64),
-                std::end   (head64),
-                std::begin (x)
-            );
+            read_array (head08, x);
 
             u64 aa = a, bb = b, cc = c;