Hash: Merge UB fix to release.

[SVN r82256]

doc/changes.qbk

@@ -150,5 +150,6 @@
 * On platforms that are known to have standard floating point, don't use the
   automatic detection of floating point functions - which can break if there
   are ambiguous overloads.
+* Fix undefined behaviour when using the binary float hash (Thomas Heller).
 
 [endsect]

include/boost/functional/hash/detail/hash_float.hpp

@@ -73,7 +73,9 @@ namespace boost
                 ptr += sizeof(std::size_t);
 
                 while(length >= sizeof(std::size_t)) {
-                    hash_float_combine(seed, *(std::size_t*) ptr);
+                    std::size_t buffer = 0;
+                    std::memcpy(&buffer, ptr, sizeof(std::size_t));
+                    hash_float_combine(seed, buffer);
                     length -= sizeof(std::size_t);
                     ptr += sizeof(std::size_t);
                 }