pgsql: docs: Improve pg_settings_get_flags docs.

docs: Improve pg_settings_get_flags docs.

In the docs, the GUC flags that pg_settings_get_flags() reported were
listed using <simplelist>. But the list was treated as separate lines
in the existing function table and didn't look good. For better view,
this commit separates the list from the table entry for
pg_settings_get_flags() and adds the table for it at the bottom of
the existing function table.

Author: Fujii Masao
Reviewed-by: Alvaro Herrera, Michael Paquier
Discussion: https://postgr.es/m/f093edf9-6e5a-b119-ee50-6a2c97c79ee8@oss.nttdata.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/f2d0c7f18b0632a93d99f373edc3d8109faffbe2

Modified Files
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doc/src/sgml/func.sgml | 64 +++++++++++++++++++++++++++++++++-----------------
1 file changed, 42 insertions(+), 22 deletions(-)