pgsql: Revert "Avoid requiring Spanish locale to test NLS infrastructur

Revert "Avoid requiring Spanish locale to test NLS infrastructure."

This reverts commit 7db6809ced4406257a80766e4109c8be8e1ea744.
That doesn't seem to work with recent (last couple of years)
glibc, and the reasons are obscure.  I can't let the farm stay
this broken for long.

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/84a3778c79c2d28b4dc281d03ef2ab019b16483b

Modified Files
--------------
src/test/regress/expected/nls.out   |  65 ++++++++++-----
src/test/regress/expected/nls_1.out |  49 ++++++-----
src/test/regress/expected/nls_2.out |  35 ++++++++
src/test/regress/po/C.po            | 161 ------------------------------------
src/test/regress/po/LINGUAS         |   2 +-
src/test/regress/po/es.po           | 159 +++++++++++++++++++++++++++++++++++
src/test/regress/regress.c          |  45 +++++-----
src/test/regress/sql/nls.sql        |  35 ++++++--
8 files changed, 314 insertions(+), 237 deletions(-)