pgsql: Implement PREPARE AS statement for ECPG.

Implement PREPARE AS statement for ECPG.

Besides implementing the new statement this change fix some issues with the
parsing of PREPARE and EXECUTE statements. The different forms of these
statements are now all handled in a ujnified way.

Author: Matsumura-san <matsumura.ryo@jp.fujitsu.com>

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/a1dc6ab465986a62b308dd1bb8da316b5ed9685a

Modified Files
--------------
src/interfaces/ecpg/ecpglib/ecpglib_extern.h       |   1 +
src/interfaces/ecpg/ecpglib/execute.c              |  82 ++-
src/interfaces/ecpg/ecpglib/prepare.c              |  54 ++
src/interfaces/ecpg/include/ecpgtype.h             |   4 +-
src/interfaces/ecpg/preproc/check_rules.pl         |   7 +-
src/interfaces/ecpg/preproc/ecpg.addons            |  66 +-
src/interfaces/ecpg/preproc/ecpg.header            |   1 +
src/interfaces/ecpg/preproc/output.c               |  24 +-
src/interfaces/ecpg/preproc/parse.pl               |   9 +-
src/interfaces/ecpg/preproc/type.h                 |   6 +
src/interfaces/ecpg/test/ecpg_schedule             |   1 +
src/interfaces/ecpg/test/expected/sql-prepareas.c  | 664 +++++++++++++++++++++
.../ecpg/test/expected/sql-prepareas.stderr        |   0
.../ecpg/test/expected/sql-prepareas.stdout        |  66 ++
src/interfaces/ecpg/test/sql/Makefile              |   3 +-
src/interfaces/ecpg/test/sql/prepareas.pgc         | 198 ++++++
16 files changed, 1163 insertions(+), 23 deletions(-)