pgsql: Add tab completion support for the WAIT FOR command

Add tab completion support for the WAIT FOR command

This commit implements tab completion for the WAIT FOR LSN command in psql.

Discussion: https://postgr.es/m/CABPTF7WnLPKcoTGCGge1dDpOieZ2HGF7OVqhNXDcRLPPdSw%3DxA%40mail.gmail.com
Author: Xuneng Zhou <xunengzhou@gmail.com>
Reviewed-by: Alexander Korotkov <aekorotkov@gmail.com>

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/a1f7f91be2c24c0a9e8d5b9e75bc43437d5476c2

Modified Files
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src/bin/psql/tab-complete.in.c | 37 ++++++++++++++++++++++++++++++++++++-
1 file changed, 36 insertions(+), 1 deletion(-)