pgsql: psql: give ^D hint for \q in place where \q is ignored

psql: give ^D hint for \q in place where \q is ignored

Also add comment on why exit/quit are not documented.

Discussion: https://postgr.es/m/[email protected]

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/91389228a1007fa3845e29e17568e52ab1726d5d

Modified Files
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src/bin/psql/mainloop.c | 27 ++++++++++++++++++++++++++-
1 file changed, 26 insertions(+), 1 deletion(-)