geometry.index test: changed rtree parameters to ensure that rtree will have at least 3 levels, added test for experimental spatial query iterator.

git-svn-id: http://svn.boost.org/svn/boost/trunk@83934 b8fc166d-592f-0410-95f2-cb63ce0dd405
geometry.index: added experimental spatial query iterator and rtree::qbegin() and rtree::qend() methods, added allocator_type to Allocators.

git-svn-id: http://svn.boost.org/svn/boost/trunk@83935 b8fc166d-592f-0410-95f2-cb63ce0dd405