The built-in clang doesn’t support value() for
`std::experimental::optional`. It however supports
dereference operator, which is basically the
same thing:
```
/clickhouse/dbms/src/DataStreams/NullableAdapterBlockInputStream.cpp:83:67: error: call to unavailable member function 'value':
res.insert({elem.column, elem.type, rename[i].value()});
~~~~~~~~~~^~~~~
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/experimental/optional:547:17: note: candidate function has been explicitly made unavailable
value_type& value()
^
/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/include/c++/v1/experimental/optional:539:33: note: candidate function has been explicitly made unavailable
constexpr value_type const& value() const
```
* Better support for disabling libmysqlclient [#CLICKHOUSE-2].
* Addition to prev. revision [#CLICKHOUSE-2].
* Addition to prev. revision [#CLICKHOUSE-2].
* partial poco support
* fix
* fix optional ssl
* servier without netssl
* fix link order
* testme
* requested changes
* throw on https listen, shutdown tip
