pgsql: Add wal_sync_method=fdatasync for Windows.

Add wal_sync_method=fdatasync for Windows.

Windows 10 gained support for flushing NTFS files with fdatasync()
semantics.  The main advantage over open_datasync (in Windows API terms
FILE_FLAG_WRITE_THROUGH) is that the latter does not flush SATA drive
caches.  The default setting is not changed, so users have to opt in to
this.

Discussion: https://postgr.es/m/CA%2BhUKGJZJVO%3DiX%2Beb-PXi2_XS9ZRqnn_4URh0NUQOwt6-_51xQ%40mail.gmail.com

Branch
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master

Details
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https://git.postgresql.org/pg/commitdiff/9430fb407bb64cc842e56fb5844265a9343dafba

Modified Files
--------------
configure                     |  6 +++++
configure.ac                  |  1 +
doc/src/sgml/wal.sgml         |  3 ++-
src/include/c.h               |  2 +-
src/include/port/win32_port.h |  6 +++++
src/include/port/win32ntdll.h | 10 +++++++-
src/port/fdatasync.c          | 53 +++++++++++++++++++++++++++++++++++++++++++
src/port/win32ntdll.c         |  6 ++++-
src/tools/msvc/Mkvcbuild.pm   |  3 ++-
src/tools/msvc/Solution.pm    |  2 +-
10 files changed, 86 insertions(+), 6 deletions(-)