msvc: add branch name and commit hash to version output

msvc: add branch name and commit hash to version output

Add a simple python script which generates header with
branch name and commit hash #defines.

While on it, fix filename in msvc-generate.vcxproj
and add proper copyright header to Makefile.mak.

Signed-off-by: Lev Stipakov <lev@openvpn.net>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <20220926064310.688-1-lstipakov@gmail.com>
URL: https://www.mail-archive.com/openvpn-devel@lists.sourceforge.net/msg25311.html
Signed-off-by: Gert Doering <gert@greenie.muc.de>