Removed IndexPMap parameter of mst_orient_normals():
* Removed IndexPMap parameter of mst_orient_normals(). Instead, mst_orient_normals() creates internaly an Index_property_map object.
* Index_property_map is a template class "index" property map, which associates a 0-based index (unsigned int) to Iter iterators.
2 specializations exist:
- if Iter is a random access iterator (typically vector and deque), get() just calls std::distance() and is very efficient;
- else, the property map allocates a std::map to store indices and get() requires a lookup in the map.
* Index_property_map is moved to an independent header Index_property_map.h but is not documented.