Make sure printtup() always sends the number of columns previously

Make sure printtup() always sends the number of columns previously
advertised in RowDescription message.  Depending on the physical tuple's
column count is not really correct, since according to heap_getattr()
conventions the tuple may be short some columns, which will automatically
get read as nulls.  Problem has been latent since forever, but was only
exposed by recent change to skip a projection step in SELECT * FROM...