handled non-simple Linestrings, for now without spikes
added a comment
fixed error in relate(), entry points seg_id replaced by other_seg_id - required for MultiLinestrings
relate(L,L) algorithm without preliminary boundaries analisys - work in progress
relate(L,L) handled one special case, still not fully working
get_turn_info_linear_linear<>::handle_first_last() method moved to better reflect calling dependency
[get_turns] fixed error in get_turn_info_linear_linear - invalid operations generated for the endpoint-internal IP for opposite segments
Merge branch 'feature/relate' of https://github.com/boostorg/geometry into feature/setops