Greatly improve speed of Delaunay when have a lot of holes.

Using part of a patch from Erik Abrahamsson, this replaces the
use of linked lists for original id tracking by Sets.
I had thought that the lists were unlikely to grow to more than
a few elements, but when the mesh has a lot of holes (whose
original ids go *outside* the hole, and therefore, most of the
mesh), this assumption can be very wrong.
On a Text regression test, the time went from 11.67s to 0.16s
with this fix. I also tested to make sure that Boolean didn't
slow down with this, and found it actually had a very slight speedup.

Using Sets exposed a dependency on the ordering of the items
in the id lists, luckily caught by a mesh intersect regression test,
so fixed that.

0 files changed, 0 insertions, 0 deletions