pgsql: Improve tab completion of ALTER INDEX/TABLE with SETSTATISTICS

Improve tab completion of ALTER INDEX/TABLE with SET STATISTICS in psql

This fixes two issues with the completion of ALTER TABLE and ALTER INDEX
after SET STATISTICS is typed, trying to suggest schema objects while
the grammar only allows integers.

The tab completion of ALTER INDEX is made smarter by handling properly
more patterns.  COLUMN is an optional keyword, but as no column numbers
can be suggested yet as possible input simply adjust the completion so
as no incorrect queries are generated.

Author: Michael Paquier
Reviewed-by: Tatsuro Yamada
Discussion: https://postgr.es/m/20181219092255.GC680@paquier.xyz

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f89ae34ab8b4d9e9ce8af6bd889238b0ccff17cb

Modified Files
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src/bin/psql/tab-complete.c | 17 +++++++++++++++++
1 file changed, 17 insertions(+)