pgsql: Report more information if pg_perm_setlocale() fails at startup.

Report more information if pg_perm_setlocale() fails at startup.

We don't know why a few Windows users have seen this fail, but the
taciturnity of the error message certainly isn't helping debug it.
Let's at least find out which LC category isn't working.

Branch
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REL9_4_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/abdeb3504d079eb622264c248a0eff4a86d2614e

Modified Files
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src/backend/main/main.c |   27 ++++++++++++++-------------
1 file changed, 14 insertions(+), 13 deletions(-)