Add bitsery trait for Boost.Container small_vector

I was going to implement these myself since we don't need them to be
contiguous like Boost's implementation is, but this is much easier of
course.

src/common/bitsery/traits/small-vector.h

@@ -0,0 +1,44 @@
+// yabridge: a Wine VST bridge
+// Copyright (C) 2020-2021 Robbert van der Helm
+//
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+//
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+//
+// You should have received a copy of the GNU General Public License
+// along with this program.  If not, see <https://www.gnu.org/licenses/>.
+
+#pragma once
+
+#include <bitsery/traits/core/std_defaults.h>
+#include <boost/container/detail/is_contiguous_container.hpp>
+#include <boost/container/small_vector.hpp>
+
+namespace bitsery {
+namespace traits {
+
+template <typename T, size_t N, typename Allocator>
+struct ContainerTraits<boost::container::small_vector<T, N, Allocator>>
+    : public StdContainer<boost::container::small_vector<T, N, Allocator>,
+                          true,
+                          true> {
+    // Unlike `std::vector`, I'm pretty sure
+    // `boost::container::small_vector<bool, N>` is contiguous. So hopefully
+    // this assertion does its thing.
+    static_assert(boost::container::dtl::is_contiguous_container<
+                  boost::container::small_vector<T, N, Allocator>>::value);
+};
+
+template <typename T, size_t N, typename Allocator>
+struct BufferAdapterTraits<boost::container::small_vector<T, N, Allocator>>
+    : public StdContainerForBufferAdapter<
+          boost::container::small_vector<T, N, Allocator>> {};
+
+}  // namespace traits
+}  // namespace bitsery