GLFW_SCALE_TO_MONITOR had no effect on Windows 8.1 up to and including
Windows 10 version 1607 (Anniversary Update), despite those having
support for per-monitor DPI.
That done was to avoid handling systems that have non-client scaling,
introduced in Windows 10 version 1607, without reliable overriding of
the new window size, introduced in Windows 10 version 1703 (Creators
Update). Both are needed to keep the content area at a fixed size for
windows that have GLFW_SCALE_TO_MONITOR disabled.
This change enables window rescaling on Windows 8.1 and all later
versions but disables non-client scaling for unscaled windows on Windows
10 version 1607. Versions after 1607 are unaffected.
Fixes#1511.
(cherry picked from commit 729c9988d0)