Windows cross-compile cleanup

Windows cross-compile cleanup

It should be sufficient to just try to see if socklen_t is defined.
Next, on all platforms it would be int in all other platforms.
And, there is no need to check for the type in monolitic environment
like Windows, as it will be always the same.

Currently it fails cross compile windows in mingw-w64 compiler, as
winsock.h is as follows:
   """
     /* define WINSOCK_API_LINKAGE and WSAAPI for less
      * diff output between winsock.h and winsock2.h, but
      * remember to undefine them at the end of file */
   """
And the macro uses these macros which are internal winsock macros and
should not be used anyway.

Also, when did the autodefs.h went mandatory? Why is it in
tap-win32/common.h while no constant is actually used?

The use of WSA_IO_INCOMPLETE without including winsock2.h is invalid!
Look at http://msdn.microsoft.com/en-us/library/aa921087.aspx

Signed-off-by: Alon Bar-Lev <alon.barlev@gmail.com>
Acked-by: James Yonan <james@openvpn.net>
Signed-off-by: David Sommerseth <davids@redhat.com>