#1851 GPVAL_SYSNAME does not give correct version number on windows 10.

[Tatsuro MATSUOKA]

GPVAL_SYSNAME is introduced to the cvs tree as the below:
https://sourceforge.net/p/gnuplot/feature-requests/422/
On windows, version information is aquired external findversion.h, in which VerifyVersionInfo is used.
On its site
https://msdn.microsoft.com/ja-jp/library/windows/desktop/ms725492(v=vs.85).aspx
VerifyVersionInfo returns false when called by applications that do not have a compatibility manifest for Windows 8.1 or Windows 10 if the lpVersionInfo parameter is set so that it specifies Windows 8.1 or Windows 10, even when the current operating system version is Windows 8.1 or Windows 10.

So we need to add compatibility tages to the manifest files.

I have prepared a patch. (I thank to Prof. Kakuto for valuable advises.)

[Bastian Märkisch]

Applied to CVS. Thanks.

[Tatsuro MATSUOKA]

I have confirmed that change in manifest and your change for get version code worked.
Thanks!