Replace stdx::optional and stdx::string_view with the C++ std
counterparts.
Some instances of boost::variant were also replaced with std::variant,
namely those that called seastar::visit.
Scylla now requires GCC 8 to compile.
Signed-off-by: Duarte Nunes <duarte@scylladb.com>
Message-Id: <20190108111141.5369-1-duarte@scylladb.com>
The as_json_function class is not registered as a function, but we can
still keep it cql3/functions, as per its namespace, to reduce the size
of select_statement.cc.
Message-Id: <20181002132637.30233-1-penberg@scylladb.com>