pgsql: Fix some -Wcast-qual warnings

Fix some -Wcast-qual warnings

This fixes some warnings from -Wcast-qual that are easy to fix,
without using unconstify or the like.

Reviewed-by: Bertrand Drouvot <bertranddrouvot(dot)pg(at)gmail(dot)com>
Discussion: https://www.postgresql.org/message-id/990c9117-b013-4026-aaf5-261fe2832c3d%40eisentraut.org

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/3f9886298052802258261e1bdcd3f1dd0e8399b9

Modified Files
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src/backend/access/gin/ginbulk.c | 2 +-
src/backend/postmaster/launch_backend.c | 12 ++++++------
src/backend/utils/adt/xml.c | 5 +++--
src/backend/utils/error/elog.c | 7 +++++--
src/common/jsonapi.c | 6 +++---
src/fe_utils/astreamer_lz4.c | 12 ++++++------
src/include/access/gin_private.h | 2 +-
src/include/port/pg_lfind.h | 4 ++--
src/include/postmaster/postmaster.h | 2 +-
src/interfaces/ecpg/preproc/parser.c | 17 +++++++++++------
10 files changed, 39 insertions(+), 30 deletions(-)