geometry.index: added stl container-like typedefs in rtree (reference, pointer, etc.), added type-erased iterator - currently may be enabled by define.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84071 b8fc166d-592f-0410-95f2-cb63ce0dd405
geometry.index test: added test of type-erased iterators - currently may be enabled by define.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84072 b8fc166d-592f-0410-95f2-cb63ce0dd405