pgsql: Improve pg_dump/pg_dumpall help synopses and terminology

Improve pg_dump/pg_dumpall help synopses and terminology

Increase consistency of --help and man page synopses between pg_dump
and pg_dumpall. These should now be very similar, as pg_dumpall can
now also produce non-text dump output. But actually, they had drifted
further apart.

- Use verb "export" consistently, instead of "dump" or "extract".
- Use "SQL script" instead of just "script" or "text file".
- Maintain consistent distinction between SQL script and other
formats/archives (which is relevant for pg_restore).

Reviewed-by: Robert Treat <rob(at)xzilla(dot)net>
Discussion: https://www.postgresql.org/message-id/flat/3f71d8a7-095b-4829-9b0b-fce09e9866b3%40eisentraut.org

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/dec6643487bbed8f5d771e9b9aff772e5c711d4d

Modified Files
--------------
doc/src/sgml/ref/pg_dump.sgml | 2 +-
doc/src/sgml/ref/pg_dumpall.sgml | 7 +++++--
doc/src/sgml/ref/pg_restore.sgml | 4 ++--
src/bin/pg_dump/pg_dump.c | 2 +-
src/bin/pg_dump/pg_dumpall.c | 2 +-
5 files changed, 10 insertions(+), 7 deletions(-)