Support for boost 1.71:

* replace boost::beast::detail::iequals with boost::iequals
* replace deprecated `buffers` function with `make_printable`
* replace boost::beast::detail::ascii_tolower with lambda
* add missing includes

src/ripple/nodestore/impl/Shard.cpp

@@ -57,6 +57,7 @@ Shard::Shard(
 bool
 Shard::open(Scheduler& scheduler, nudb::context& ctx)
 {
+    using namespace boost::filesystem;
     std::lock_guard lock(mutex_);
     assert(!backend_);