Consume all results after a COPY

Closes #119.  This patch feels wrong, but it fixes the test case.
It'll have to do for now,  as a quick fix.

Among other things,  I believe that PQ.getResult can block. Ugh.

This whole issue has definitely highlighted some of the annoyances
I have with libpq,  but at least it's still fantastically better than
ODBC.