[get_turns] fix for MultiLinestrings containing Ls with equal points

In this case no sections were generated for those "empty" Linestrings but if there were some sections already generated they could be marked as last_non_duplicated.
[get_turns] Fix turns dumplication for L/L.

Change the ignoring check calculation in get_turn_info_for_endpoint.
Add additional parameters to the second version of collinear_opposite<>::apply() defining if the pk and/or qk are valid (in other words current segment is NOT the last one).
Also make ignoring check for last endpoint in L/A more clear.