pgsql: Avoid possibly-unsafe use of Windows' FormatMessage() function.

Avoid possibly-unsafe use of Windows' FormatMessage() function.

Whenever this function is used with the FORMAT_MESSAGE_FROM_SYSTEM flag,
it's good practice to include FORMAT_MESSAGE_IGNORE_INSERTS as well.
Otherwise, if the message contains any %n insertion markers, the function
will try to fetch argument strings to substitute --- which we are not
passing, possibly leading to a crash. This is exactly analogous to the
rule about not giving printf() a format string you're not in control of.

Noted and patched by Christian Ullrich.
Back-patch to all supported branches.

Branch
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REL9_5_STABLE

Details
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http://git.postgresql.org/pg/commitdiff/491e847380740dac54d4ecae820261bbaa8aee44

Modified Files
--------------
src/backend/libpq/auth.c | 4 +++-
src/backend/port/win32/socket.c | 4 +++-
src/interfaces/libpq/fe-auth.c | 4 +++-
src/port/dirmod.c | 8 ++++++--
4 files changed, 15 insertions(+), 5 deletions(-)