[get_turns] Add handling of spikes for L/L for endpoints
[relate][get_turns] Add the support for spikes in relate(L/L). Fix errors in get_turns L/L.

Some asserts are invalid when 'x' operation can be somewhere in the middle (boundary_checker).
boundary_checker::is_boundary() function removed since it's not used anywhere.
Errors in get_turns are related to the handling of touches turn. t,i/i must be handled and is_collinear must be set in operations for spikes.