geometry.index: made changes required to allow copying of query iterators - geometries objects are now wrapped in predicates instead of const references, pointers to const translator instead of const references are stored in queries incremental visitors.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84057 b8fc166d-592f-0410-95f2-cb63ce0dd405
geometry.index example: experimental features moved from benchmark to benchmark_experimental, added type-erased iterators to it.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84058 b8fc166d-592f-0410-95f2-cb63ce0dd405