Removed portal test from demo.cpp
Added new debug draw mode (regions connections).
Tweaked several debug draw modes to be more illustrative.
Added checks in the Detour code to allow to call the API even if the initialization failed.
Rewrote fixup contours, now should handle all cases.
Added few more debug draw modes for the demo.
Changed the vertex welding to cope with slight imprecision in y-direction.
