handle Windows unicode paths

handle Windows unicode paths

Openvpn for Windows is not compiled as a Unicode binary and thus cannot
handle paths which contain non-ASCII characters using the argv vector.
Characters that are not present in the system codepage are simply replaced
with a question mark, e.g. if started as 'openvpn --config домой.ovpn'
the file '?????.ovpn' is tried to be opened as configuration.

The same applies to paths in config files which need to be UTF-8
encoded if they contain non ASCII characters. The option line
'key лев.pem' will lead to openvpn trying to open 'лев.pem' on a
system with codepage 1252.

This patch makes openvpn read the command line in UCS-2 and convert
it to UTF-8 internally. Windows stores names in the filesystem in UCS-2.
When using a paths openvpn converts it from UTF-8 to UCS-2 and uses the
wide character Windows API function.

Signed-off-by: Heiko Hund <heiko.hund@sophos.com>
Acked-by: David Sommerseth <davids@redhat.com>
Signed-off-by: David Sommerseth <davids@redhat.com>