Wrong turns generated by get_turns() for Linear spikes.

[awulkiew]

1. For L/A:

   "LINESTRING(7 8, 6 10, 10 2)"
   "POLYGON((0 0,0 10,10 10,10 0,0 0))"
   
   "LINESTRING(7 8, 6 10, 11 0)"
   "POLYGON((0 0,0 10,10 10,10 0,0 0))"
   

for intersection point (6 10) u/u is generated instead of i/u.

2. For L/L:

   "LINESTRING(6 0,0 0,5 0)"
   "LINESTRING(2 0,0 0,-10 0)"
   

for intersection point (0 0) only one, wrong turn is generated (a spike is not detected as a spike).

3. For L/L

   "LINESTRING(-7 -8,3 0,4 -1,-7 10)"
   "LINESTRING(-5 -4,3 0,4 -1,7 -4,2 -1)"
   

similar to the above.

[awulkiew]

Fixes:

1. ​https://github.com/boostorg/geometry/commit/810030309238309a4c258d77a50c62a4b6994b99
2. ​https://github.com/boostorg/geometry/commit/3e367f9f6df16b0a15519bec045251a2754e9e23
3. ​https://github.com/boostorg/geometry/commit/5c73173d60ac41ed79cd2e60760ccc55cf298173