<functional> support
The following functions from <functional> are overloaded:
#include <boost/decimal/hash.hpp>
namespace std {
template <>
struct hash<boost::decimal::decimal32_t>;
template <>
struct hash<boost::decimal::decimal_fast32_t>;
template <>
struct hash<boost::decimal::decimal64_t>;
template <>
struct hash<boost::decimal::decimal_fast64_t>;
template <>
struct hash<boost::decimal::decimal128_t>;
template <>
struct hash<boost::decimal::decimal_fast128_t>;
} //namespace std