The attached patch completes the following TODO item:

    * Generate failure on short COPY lines rather than pad NULLs

I also restructed a lot of the existing COPY code, did some code
review on the column list patch sent in by Brent Verner a little
while ago, and added some regression tests. I also added an
explicit check (and resultant error) for extra data before
the end-of-line.

Neil Conway