Badly constructed OSM intersections can create OSRM intersection
views that have no valid turns.
The guidance code for segregated intersections tries to look
ahead to the second intersection to ensure lanes are announced
intuitively.
Currently, OSRM assumes there are always turns at the second
intersection that we should consider. This commit corrects
this assumption so that it can now handle badly constructed
OSM intersections with no turns.
- moves collapse into a dedicated set of functions / files
- make collapse scenarios distinct (slight performance cost)
- reduce verbosity for short name segments (now actually working, was supposed to do so before)
