* Moved library into its own module, `container_hash`.
* Moved headers for new module name, now at: `<boost/container_hash/hash.hpp>`, `<boost/container_hash/hash_fwd.hpp>`, `<boost/container_hash/extensions.hpp>`.
* Added forwarding headers to support the old headers locations.
* Support `std::string_view`, `std::error_code`, `std::error_condition`, `std::optional`, `std::variant`, `std::monostate` where available.
* Update include paths from other Boost libraries.
* Manually write out tuple overloads, rather than using the preprocessor to generate them. Should improve usability, due to better error messages, and easier debugging.
* Avoid float comparison warning when using Clang - this workaround was already in place for GCC, and was used when Clang pretends to be GCC, but the warning was appearing when running Clang in other contexts.
== Boost 1.65.0
* Support for `char16_t`, `char32_t`, `u16string`, `u32string`
* Fix for recent versions of Visual {cpp} which have removed `std::unary_function` and `std::binary_function` (https://svn.boost.org/trac/boost/ticket/12353[#12353]).
* Only define hash for `std::wstring` when we know we have a `wchar_t`. Otherwise there's a compile error as there's no overload for hashing the characters in wide strings (https://svn.boost.org/trac/boost/ticket/8552[#8552]).
* Add support for `boost::int128_type` and `boost::uint128_type` where available - currently only `{int128}` and `unsigned {int128}` on some versions of gcc.
* On platforms that are known to have the standard floating point functions, don't use automatic detection - which can break if there are ambiguous overloads.
* Fix undefined behaviour when using the binary `float` hash (Thomas Heller).
* Add option to prevent implicit conversions when calling `hash_value` by defining `BOOST_HASH_NO_IMPLICIT_CASTS`. When using `boost::hash` for a type that does not have `hash_value` declared but does have an implicit conversion to a type that does, it would use that implicit conversion to hash it. Which can sometimes go very wrong, e.g. using a conversion to `bool` and only hashing to 2 possible values. Since fixing this is a breaking change and was only approached quite late in the release cycle with little discussion it's opt-in for now. This, or something like it, will become the default in a future version.
* https://svn.boost.org/trac/boost/ticket/3866[Ticket 3866]: Don't foward declare containers when using gcc's parallel library, allow user to stop forward declaration by defining the `BOOST_DETAIL_NO_CONTAINER_FWD` macro.
* https://svn.boost.org/trac/boost/ticket/4038[Ticket 4038]: Avoid hashing `0.5` and `0` to the same number.
* Move the `hash_fwd.hpp` implementation into the hash subdirectory, leaving a forwarding header in the old location. You should still use the old location, the new location is mainly for implementation and possible modularization.
* Changed the warnings in the deprecated headers from 1.34.0 to errors. These will be removed in a future version of Boost.
* Moved detail headers out of `boost/container_hash/detail`, since they are part of `functional/hash`, not `container_hash`. `boost/container_hash/detail/container_fwd.hpp` has been moved to `boost/detail/container_fwd.hpp` as it's used outside of this library, the others have been moved to `boost/functional/hash/detail`.
* http://svn.boost.org/trac/boost/ticket/2264[Ticket 2264]: In Visual {cpp}, always use C99 float functions for long double and float as the {cpp} overloads aren't always availables.
** Fits more information into each combine loop, which can reduce the the number of times combine is called and hopefully give a better quality hash function.
** Improved the algorithm for hashing floating point numbers.
** On Cygwin use a binary hash function for floating point numbers, as Cygwin doesn't have decent floating point functions for `long double`.
** Never uses `fpclass` which doesn't support `long double`.
