make CGEN a less moving target?

[Doug Evans]

Frank Ch. Eigler writes:
 > The most important value is the base-insn-size.  This should be
 > large enough to include all opcode-like bits in the longest
 > instruction, so most likely 16 or even 32 for this chip.  Having
 > real instructions that are shorter than that is not a problem.

If the definition of base-insn-size has been changed to this that's a bummer.
When did this go in?