pgsql: - EXECUTE can return NOT FOUND so it should be checked here too.

Log Message:
-----------
- EXECUTE can return NOT FOUND so it should be checked here too.
- Changed regression test accordingly.

Modified Files:
--------------
    pgsql/src/interfaces/ecpg:
        ChangeLog (r1.371 -> r1.372)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/ChangeLog?r1=1.371&r2=1.372)
    pgsql/src/interfaces/ecpg/preproc:
        preproc.y (r1.359 -> r1.360)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/preproc/preproc.y?r1=1.359&r2=1.360)
    pgsql/src/interfaces/ecpg/test/expected:
        sql-execute.c (r1.10 -> r1.11)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-execute.c?r1=1.10&r2=1.11)
        sql-execute.stderr (r1.4 -> r1.5)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-execute.stderr?r1=1.4&r2=1.5)
        sql-execute.stdout (r1.1 -> r1.2)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/sql-execute.stdout?r1=1.1&r2=1.2)
        thread-prep.c (r1.4 -> r1.5)

(http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/expected/thread-prep.c?r1=1.4&r2=1.5)
    pgsql/src/interfaces/ecpg/test/sql:
        execute.pgc (r1.2 -> r1.3)
        (http://developer.postgresql.org/cvsweb.cgi/pgsql/src/interfaces/ecpg/test/sql/execute.pgc?r1=1.2&r2=1.3)