New hash_append robust container hash function framework:

* is_contiguous_hashable trait identifies optimizable types
* hash_append() function overloads for basic types:
  - scalars, floats
  - array, C array
  - pair, tuple
  - boost array and tuple (if configured)
* Provided Spooky hash wrapper for use with hash_append
* Use hash_append in hardened_hash and other places
* New Utility meta functions for working with variadics:
  - static_and
  - static_sum
* Added type_name utility function for diagnostics
* hash_metrics suite of functions to evalulate hash functions
* Test suites to measure hash function performance
* Various fixes

beast/crypto/UnsignedInteger.h

@@ -60,14 +60,6 @@ public:
     typedef value_type*        iterator;
     typedef value_type const*  const_iterator;
 
-    void
-    hash_combine (std::size_t& seed) const noexcept
-    {
-        std::size_t result;
-        Murmur::Hash (get(), size, seed, &result);
-        seed = result;
-    }
-
     /** Hardened hash function for use with hash based containers.
         The seed is used to make the hash unpredictable. This prevents
         attackers from exploiting crafted inputs to produce degenerate