patch 9.2.0867: MS-Windows: messages are not in the display language

patch 9.2.0867: MS-Windows: messages are not in the display language

Problem:  On MS-Windows the messages use the language of the regional
          format, not the language that Windows is displayed in
          (Markus Nißl)
Solution: Use the display language for the messages, with the other
          preferred languages as fall back.  Make ":language messages"
          overrule it (Hirohito Higashi).

fixes:  #20855
closes: #20860

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Hirohito Higashi <h.east.727@gmail.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>