Sun Oct 10 16:12:37 CEST 2010

EX on top of CELL? NO -> split EX code

It doesn't seem to make much sense to port EX on top of CELL.  It
makes more sense to centralize pair processing code since it is used
in LEAF, EX, CELL (and PF).

1. It seems that most code in EX can be auto-generated: it's really
   mostly wrappers.  The beef is in LEAF anyway.

2. The PAIR processing code can be abstracted and possibly reused in
   LEAF for its linear / RC cells.