pgsql: Improve ALTER TABLE documentation

Improve ALTER TABLE documentation

The ALTER TABLE documentation wasn't terribly clear when it came to
which commands could be combined together and what it meant when they
were.

In particular, SET TABLESPACE *can* be combined with other commands,
when it's operating against a single table, but not when multiple tables
are being moved with ALL IN TABLESPACE. Further, the actions are
applied together but not really in 'parallel', at least today.

Pointed out by: Amit Langote

Improved wording from Tom.

Back-patch to 9.4, where the ALL IN TABLESPACE option was added.

Discussion: https://www.postgresql.org/message-id/14c535b4-13ef-0590-1b98-76af355a0763%40lab.ntt.co.jp

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/ec2bc3264ef007e6d7b6463029de689273161336

Modified Files
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doc/src/sgml/ref/alter_table.sgml | 8 ++++----
1 file changed, 4 insertions(+), 4 deletions(-)