pgsql: Sync ECPG's CREATE TABLE AS statement with backend's.

Sync ECPG's CREATE TABLE AS statement with backend's.

Author: Higuchi-san ("Higuchi, Daisuke" <higuchi.daisuke@jp.fujitsu.com>)

Branch
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REL_11_STABLE

Details
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https://git.postgresql.org/pg/commitdiff/3530c508ca68d47cd5a30a1a28f99bdd23cb90c8

Modified Files
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src/interfaces/ecpg/preproc/ecpg.trailer           |   9 +-
src/interfaces/ecpg/test/ecpg_schedule             |   1 +
.../ecpg/test/expected/sql-createtableas.c         | 164 +++++++++++++++++++++
.../ecpg/test/expected/sql-createtableas.stderr    |  66 +++++++++
.../ecpg/test/expected/sql-createtableas.stdout    |   2 +
src/interfaces/ecpg/test/sql/Makefile              |   1 +
src/interfaces/ecpg/test/sql/createtableas.pgc     |  41 ++++++
7 files changed, 283 insertions(+), 1 deletion(-)