efl_net_*: improve WIN32.

efl_net_*: improve WIN32.

Thanks to vtorri for poiting out about close() is not the correct
socket function, we should use closesocket() instead.

Also defined SOCKET to int on Linux so we can use the same 'type' and
avoid lots of ifdef in our code. On Windows it's unsigned, thus would
cause some warnings about incorrect signed comparison.