[geometry] avoid warnings for multi-line comments and unused var in new sources

git-svn-id: http://svn.boost.org/svn/boost/trunk@86581 b8fc166d-592f-0410-95f2-cb63ce0dd405
Added a test for add_value manipulator. Added operator[] overloads for attibute_name as key.

git-svn-id: http://svn.boost.org/svn/boost/trunk@86582 b8fc166d-592f-0410-95f2-cb63ce0dd405
Fix an uninitialized member in a default-initialized split_iterator; Refs #9335

git-svn-id: http://svn.boost.org/svn/boost/trunk@86583 b8fc166d-592f-0410-95f2-cb63ce0dd405