Fix psql's \copy to not insert spaces around dots and commas in the text of

Fix psql's \copy to not insert spaces around dots and commas in the text of
the SELECT query in \copy (SELECT ...) commands.  This is unnecessary and
breaks numeric literals, as seen in bug #5411 from Vitalii Tymchyshyn.

This change has already been made in passing in HEAD; backpatch to 8.2
through 8.4 (earlier releases don't have COPY (SELECT ...) at all).