This gives us more flexibility than using the intransparent FwpmIPsecTunnelAdd,
and fixes the issues we have seen with trap policies. Forward filters are
still missing, but required for site-to-site tunnels.
While MinGW declares all the required symbols, some of them are missing in the
library files. We provide missing variables locally, functions get a stub
that call the GetProcAddress()ed function from the DLL.
Also some MinGW headers define some enum values incorrectly, we overload these
using defines.
Martin Willi