win32: add missing include header

win32: add missing include header

Commit 5a571fb0 ("Move utility function from win32.c to win32-util.c")
moved some functions from win32.[ch] to a new win32-util.[ch], but missed
adding new include header, which results in compilation errors like:

    >cryptoapi.c
    >C:\Users\lev\Projects\openvpn\src\openvpn\cryptoapi.c(755,53): error
C2220: the following warning is treated as an error
    >C:\Users\lev\Projects\openvpn\src\openvpn\cryptoapi.c(755,53):
warning C4047: '=': 'const void *' differs in levels of indirection from
'int'

Fix by adding #include "win32-util.h" to "win32.h".

While on it, update vcxproj.filters with a new header so that
it looks "correct" in VS project view.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20210513140039.265-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg22379.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>