Re: pg_dump multi VALUES INSERT

Pushed, thanks!

If anyone is feeling inspired, one additional test we could use is
--rows-per-insert together with --on-conflict-do-nothing.

I made a couple of edits to v17 before pushing,

* rename strtol endptr variable so that it can be used by other strtol
calls, if we ever have them

* use pre-increment in if() test rather than separate line with
post-increment; reduces line count by 2.

* reworded --help output to: "number of rows per INSERT; implies --inserts"

* added one row-ending archputs(")") which makes the repeated
statement-ending archputs() match exactly.  (Negligible slowdown, I
expect)

* moved DUMP_DEFAULT_ROWS_PER_INSERT to pg_dump.c from pg_dump.h

* there was a space-before-comma in an error message, even immortalized
in the test expected output.

* remove the rows_per_insert_zero_col dump output file; the test can be
done by adding the table to the rows_per_insert file.  Add one more row
to that zero-column table, so that the INSERT .. DEFAULT VALUES test
verifies the case with more than one row.

* changed the rows_per_insert to use 4 rows per insert rather than
three; that improves coverage (table had 9 rows so it was always hitting
the case where a full statement is emitted.)

-- 
Álvaro Herrera                https://www.2ndQuadrant.com/
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