Moved checked deleters into internal namespace to block unintended ADL.

This prevents adding namespace boost to ADL when the deleters are used
in template parameters, e.g. in std::unique_ptr.

test/Jamfile.v2

@@ -39,6 +39,10 @@ compile-fail checked_delete_fail.cpp
   : $(warnings-as-errors-off) ;
 compile-fail checked_delete_fail2.cpp
   : $(warnings-as-errors-off) ;
+compile-fail checked_deleter_compile_fail_adl.cpp
+  : $(warnings-as-errors-off) ;
+compile-fail checked_array_deleter_compile_fail_adl.cpp
+  : $(warnings-as-errors-off) ;
 
 compile ref_ct_test.cpp ;
 run ref_test.cpp ;

test/checked_array_deleter_compile_fail_adl.cpp

@@ -0,0 +1,30 @@
+/*
+ *             Copyright Andrey Semashev 2024.
+ * Distributed under the Boost Software License, Version 1.0.
+ *    (See accompanying file LICENSE_1_0.txt or copy at
+ *          http://www.boost.org/LICENSE_1_0.txt)
+ */
+/*!
+ * \file   checked_array_deleter_compile_fail_adl.cpp
+ * \author Andrey Semashev
+ * \date   07.02.2024
+ *
+ * This file tests that \c boost::checked_array_deleter doesn't bring namespace
+ * \c boost into ADL.
+ */
+
+#include <boost/core/checked_delete.hpp>
+
+namespace boost {
+
+void check_adl(checked_array_deleter< int > const&)
+{
+}
+
+} // namespace boost
+
+int main()
+{
+    // Must not find boost::check_adl
+    check_adl(boost::checked_array_deleter< int >());
+}

test/checked_deleter_compile_fail_adl.cpp

@@ -0,0 +1,30 @@
+/*
+ *             Copyright Andrey Semashev 2024.
+ * Distributed under the Boost Software License, Version 1.0.
+ *    (See accompanying file LICENSE_1_0.txt or copy at
+ *          http://www.boost.org/LICENSE_1_0.txt)
+ */
+/*!
+ * \file   checked_deleter_compile_fail_adl.cpp
+ * \author Andrey Semashev
+ * \date   07.02.2024
+ *
+ * This file tests that \c boost::checked_deleter doesn't bring namespace
+ * \c boost into ADL.
+ */
+
+#include <boost/core/checked_delete.hpp>
+
+namespace boost {
+
+void check_adl(checked_deleter< int > const&)
+{
+}
+
+} // namespace boost
+
+int main()
+{
+    // Must not find boost::check_adl
+    check_adl(boost::checked_deleter< int >());
+}