pgsql: Fix optional-argument handling in in-tree getopt_long().

Fix optional-argument handling in in-tree getopt_long().

If a long option that accepts an optional argument is given without
one, optind is advanced twice, and the following argument is
skipped. For example, "pg_waldump --stats --limit 5" skips --limit
and interprets "5" as a non-option, so the command complains that
it cannot location WAL file "5". The same path also returns BADARG
when optstring starts with a colon, even though nothing is missing.
To fix, handle optional arguments before the missing-argument code,
which then only needs to deal with required arguments.

This is a bug fix and could be back-patched, but since this issue
went unnoticed for 23 years, I'm not going to bother.

Author: Sehrope Sarkuni <sehrope(at)jackdb(dot)com>
Reviewed-by: solai v <solai(dot)cdac(at)gmail(dot)com>
Discussion: https://postgr.es/m/CAH7T-arxDuVCSkorO%3Dk7%2BM-_JV0JFzMpN_EtKMyD2K0RDqZ2OA%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/61aa17b92eab017d64419c19fa466d72a509d016

Modified Files
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src/bin/pg_waldump/t/001_basic.pl | 3 +--
src/port/getopt_long.c | 11 +++++------
2 files changed, 6 insertions(+), 8 deletions(-)