Simplify index documentation and add author information

doc/null_deleter.qbk

@@ -5,7 +5,15 @@
  / file LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
  /]
 
-[section:null_deleter Header <boost/core/null_deleter.hpp>]
+[section:null_deleter null_deleter]
+
+[section Authors]
+
+* Andrey Semashev
+
+[endsect]
+
+[section Header <boost/core/null_deleter.hpp>]
 
 The header `<boost/core/null_deleter.hpp>` defines the `boost::null_deleter` function object,
 which can be used as a deleter with smart pointers such as `unique_ptr` or `shared_ptr`. The
@@ -20,3 +28,5 @@ Example
     }
 
 [endsect]
+
+[endsect]