pgsql: Replace pointer comparisons and assignments to literal zero with

Replace pointer comparisons and assignments to literal zero with NULL

While 0 is technically correct, NULL is the semantically appropriate
choice for pointers.

Author: Bertrand Drouvot <bertranddrouvot.pg@gmail.com>
Discussion: /messages/by-id/aS1AYnZmuRZ8g+5G@ip-10-97-1-34.eu-west-3.compute.internal

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/ec782f56b0c30ef493e8356b46e1131612f01d9f

Modified Files
--------------
src/backend/nodes/copyfuncs.c | 2 +-
src/backend/postmaster/postmaster.c | 2 +-
src/backend/utils/adt/pg_locale.c | 4 ++--
src/backend/utils/adt/timestamp.c | 2 +-
src/interfaces/ecpg/ecpglib/prepare.c | 2 +-
5 files changed, 6 insertions(+), 6 deletions(-)