Clean up edge_def's crossing_edge field

[David Edelsohn]

Caroline> At the time you asked me to change from using a boolean field into
Caroline> wrapping this into the flags fields, I explained that I considered that to
Caroline> be a pure matter of taste, that there was no pressing technical reason to
Caroline> make such a change, and that I wanted to focus first on fixing potential
Caroline> correctness issues.

	The changes are not just a matter of taste, they are issues of
style and maintainability.  Feedback from other developers is not
something that you unilaterally can decide to defer.  It was wrong of
Geoff to approve your patch without all of the feedback having been
addressed. 

	If you do not respect comments from other developers and
maintainers, then the lack of attention to your patch submissions should
not come as a surprise.

David