pgsql: ecpg: add cross-checks to parse.pl for usage of internal tables.

ecpg: add cross-checks to parse.pl for usage of internal tables.

parse.pl contains several constant tables that describe tweaks
to be made to the backend grammar. In the same spirit as
00b0e7204, add cross-checks that each table entry is used at
least once (or exactly once if that's appropriate). This should
help catch cases where adjustments to the backend grammar cause
a table entry not to match as expected.

Per suggestion from Michael Paquier.

Discussion: https://postgr.es/m/ZsLVbjsc5x5Saesg@paquier.xyz

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/d2f41b4621de6d0e9eeaa4ea1d60cad190406f5e

Modified Files
--------------
src/interfaces/ecpg/preproc/parse.pl | 41 ++++++++++++++++++++++++++++++++++--
1 file changed, 39 insertions(+), 2 deletions(-)