[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.
Merge branch 'develop' of https://github.com/boostorg/geometry into feature/setops
[set ops] removing duplicate turns is disabled now; no need for this, after Adam's fix;