Add rw_spinlock tests

test/cfoa/rw_spinlock_test4.cpp

@@ -0,0 +1,29 @@
+// Copyright 2023 Peter Dimov
+// Distributed under the Boost Software License, Version 1.0.
+// https://www.boost.org/LICENSE_1_0.txt
+
+#include <boost/unordered/detail/foa/rw_spinlock.hpp>
+#include <boost/compat/shared_lock.hpp>
+#include <mutex>
+
+using boost::unordered::detail::foa::rw_spinlock;
+
+static rw_spinlock sp;
+static rw_spinlock sp2;
+
+int main()
+{
+    sp.lock();
+    sp2.lock_shared();
+    sp2.lock_shared();
+
+    sp.unlock();
+    sp2.unlock_shared();
+    sp2.unlock_shared();
+
+    {
+        std::lock_guard<rw_spinlock> lock( sp );
+        boost::compat::shared_lock<rw_spinlock> lock2( sp2 );
+        boost::compat::shared_lock<rw_spinlock> lock3( sp2 );
+    }
+}