Fix MinGW %d vs %lu warnings in back branches.

Fix MinGW %d vs %lu warnings in back branches.

Commit 352f6f2d used %d instead of %lu to format DWORD (unsigned long)
with psprintf().  The _WIN32_WINNT value recently changed for MinGW in
REL_15_STABLE (commit d700e8d7), so the code was suddenly being
compiled, with warnings from gcc.

The warnings were already fixed in 16+ by commits 495ed0ef and a9bc04b2
after the _WIN32_WINNT value was increase there.  14 and 13 didn't warn
because they still use a lower value for MinGW, and supported versions
of Visual Studio should compile the code in all live branches but don't
check our format string.

The change doesn't affect the result: sizeof(int) == sizeof(long) on
this platform, and the values are computed with expressions that cannot
exceed INT_MAX so were never interpreted as negative.

Back-patch the formatting change from those commits into 13-15.  This
should turn CI's 15 branch green again and stop fairywren from warning
about that on 15.

Reported-by: Andres Freund <andres@anarazel.de>
Reported-by: Peter Eisentraut <peter@eisentraut.org>
Discussion: https://postgr.es/m/t2vjrcb3bloxf5qqvxjst6r7lvrefqyecxgt2koy5ho5b5glr2%40yuupmm6whgob