geometry.index: path_intersection optimized for 2-point linestrings.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84237 b8fc166d-592f-0410-95f2-cb63ce0dd405
geometry.index test, example: updated tests and benchmark_experimental for path_intersection of 2-point linestring.

git-svn-id: http://svn.boost.org/svn/boost/trunk@84238 b8fc166d-592f-0410-95f2-cb63ce0dd405