pgsql: Add DECLARE STATEMENT command to ECPG

Add DECLARE STATEMENT command to ECPG

This command declares a SQL identifier for a SQL statement to be used in other
embedded SQL statements. The identifier is linked to a connection.

Author: Hayato Kuroda <kuroda.hayato@fujitsu.com>
Reviewed-by: Shawn Wang <shawn.wang.pg@gmail.com>
Discussion:
https://www.postgresql.org/message-id/flat/TY2PR01MB24438A52DB04E71D0E501452F5630@TY2PR01MB2443.jpnprd01.prod.outlook.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ad8305a43d1890768a613d3fb586b44f17360f29

Modified Files
--------------
doc/src/sgml/ecpg.sgml                             | 140 ++++-
src/interfaces/ecpg/preproc/ecpg.addons            |  90 +++-
src/interfaces/ecpg/preproc/ecpg.c                 |   9 +
src/interfaces/ecpg/preproc/ecpg.header            |  25 +
src/interfaces/ecpg/preproc/ecpg.trailer           |  45 +-
src/interfaces/ecpg/preproc/ecpg.type              |   1 +
src/interfaces/ecpg/preproc/preproc_extern.h       |   1 +
src/interfaces/ecpg/preproc/type.h                 |   7 +
src/interfaces/ecpg/test/ecpg_schedule             |   1 +
src/interfaces/ecpg/test/expected/sql-declare.c    | 580 +++++++++++++++++++++
.../ecpg/test/expected/sql-declare.stderr          | 286 ++++++++++
.../ecpg/test/expected/sql-declare.stdout          |  20 +
src/interfaces/ecpg/test/sql/.gitignore            |   2 +
src/interfaces/ecpg/test/sql/Makefile              |   1 +
src/interfaces/ecpg/test/sql/declare.pgc           | 207 ++++++++
15 files changed, 1398 insertions(+), 17 deletions(-)