pgsql: Fix PL/pgSQL's handling of integer ranges containing underscores

Fix PL/pgSQL's handling of integer ranges containing underscores.

Commit faff8f8e47 allowed integer literals to contain underscores, but
failed to update the lexer's "numericfail" rule. As a result, a
decimal integer literal containing underscores would fail to parse, if
used in an integer range with no whitespace after the first number,
such as "1_001..1_003" in a PL/pgSQL FOR loop.

Fix and backpatch to v16, where support for underscores in integer
literals was added.

Report and patch by Erik Wienhold.

Discussion: https://postgr.es/m/808ce947-46ec-4628-85fa-3dd600b2c154%40ewie.name

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/cd2624fd97b0c36b68da278abc5362647f69b07d

Modified Files
--------------
src/backend/parser/scan.l                |  2 +-
src/fe_utils/psqlscan.l                  |  2 +-
src/interfaces/ecpg/preproc/pgc.l        |  2 +-
src/test/regress/expected/numerology.out | 11 +++++++++++
src/test/regress/sql/numerology.sql      |  9 +++++++++
5 files changed, 23 insertions(+), 3 deletions(-)