Since standard library could have platform dependent specialized hashing functions.
Also the main idea is to let `qHash` handle whatever integer type `std::hash` returns and mix it with `seed` accordingly.
PR #18715.
most of the time hash string is not needed and InfoHash is often used as
temporaries for torrent searching in handling of torrent alerts. This
improves the creation time of Infohash
This also suppresses the following clang warning:
warning: definition of implicit copy assignment operator for 'Version<unsigned short, 2>' is deprecated because it has a user-declared copy constructor [-Wdeprecated-copy]