Annotate vpnc-script-win.js with a header documenting its exact source revision

Annotate vpnc-script-win.js with a header documenting its exact source revision

By annotating the vpnc-script-win.js included in the Windows installers
with information about the exact source revision, we will ease reporting
and reduce confusion about problems resulting from interactions between
OpenConnect and vpnc-script.

Example of the header added to vpnc-script-win.js:

    // This script matches the version found at https://gitlab.com/openconnect/vpnc-scripts/-/blob/b749c2cadc2f32e2efffa69302861f9a7d4a4e5f/vpnc-script-win.js
    // Updated on 2021-09-24 by Daniel Lenski <dlenski@gmail.com> ("Ensure that vpnc-script-win.js works even if INTERNAL_IP4_{NETADDR,NETMASK} are unset")
    //

Signed-off-by: Daniel Lenski <dlenski@gmail.com>