pgsql: Fix XMLTABLE() deparsing to quote namespace names if necessary.

Fix XMLTABLE() deparsing to quote namespace names if necessary.

When deparsing an XMLTABLE() expression, XML namespace names were not
quoted. However, since they are parsed as ColLabel tokens, some names
require double quotes to ensure that they are properly interpreted.
Fix by using quote_identifier() in the deparsing code.

Back-patch to all supported versions.

Dean Rasheed, reviewed by Tom Lane.

Discussion: https://postgr.es/m/CAEZATCXTpAS%3DncfLNTZ7YS6O5puHeLg_SUYAit%2Bcs7wsrd9Msg%40mail.gmail.com

Branch
------
REL_14_STABLE

Details
-------
https://git.postgresql.org/pg/commitdiff/dc8cd9cd0198ff1d87815e74b101b4c03754f513

Modified Files
--------------
src/backend/utils/adt/ruleutils.c | 3 ++-
src/test/regress/expected/xml.out | 10 +++++++---
src/test/regress/expected/xml_1.out | 8 +++++---
src/test/regress/expected/xml_2.out | 10 +++++++---
src/test/regress/sql/xml.sql | 8 +++++---
5 files changed, 26 insertions(+), 13 deletions(-)