Cygwin: cleanup header including within network-releated files

* Rearrange includes and drop unneccessary ones.

* Don't pull in cygwin/socket.h into sys/un.h just to get
  sa_family_t.  Include sys/types.h and use __sa_family_t instead.

* start including Windows headers using the w32api/ path prefix

Signed-off-by: Corinna Vinschen <corinna@vinschen.de>

winsup/cygwin/fhandler_procnet.cc

@@ -16,21 +16,15 @@ details. */
 #undef u_long
 #define u_long __ms_u_long
 #endif
-#include <ws2tcpip.h>
-#include <iphlpapi.h>
+#include <w32api/ws2tcpip.h>
+#include <w32api/iphlpapi.h>
+#include <asm/byteorder.h>
+#include <stdio.h>
 #include "cygerrno.h"
-#include "security.h"
 #include "path.h"
 #include "fhandler.h"
 #include "fhandler_virtual.h"
 #include "dtable.h"
-#include "cygheap.h"
-#include <asm/byteorder.h>
-
-#define _COMPILING_NEWLIB
-#include <dirent.h>
-#include <stdio.h>
-#include <stdlib.h>
 
 bool get_adapters_addresses (PIP_ADAPTER_ADDRESSES *pa0, ULONG family);