Several \d variants don't put a row count at the end of their tables,
which means that atmsort doesn't stop sorting output until it finds a
row count somewhere later. Some tests are having their diff output
horribly mangled because of this, which makes debugging difficult.

When we see a \d command, try to apply more heuristics for finding the
end of a table. In addition to ending at a row count, end table sorting
whenever we find a line that doesn't have the same number of column
separators as the table header. If we don't have a table header, still
attempt to end table sorting at a blank line.

extprotocol's test output order must be fixed as a result. Put the
"External options" line where psql actually prints it, after "Format
options".