Split vnet driver to generic vnet part, tap and file interfaces

Fix most compilation issues of umka_shell on Windows(R)(TM), not all
of them.

windows/io_async.c

@@ -0,0 +1,51 @@
+/*
+    SPDX-License-Identifier: GPL-2.0-or-later
+
+    UMKa - User-Mode KolibriOS developer tools
+    io_async - input/output platform specific code
+
+    Copyright (C) 2023  Ivan Baravy <dunkaist@gmail.com>
+*/
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <inttypes.h>
+#include "umka.h"
+
+#define QUEUE_DEPTH 1
+
+#define read_barrier()  __asm__ __volatile__("":::"memory")
+#define write_barrier() __asm__ __volatile__("":::"memory")
+
+#define MAX(x, y) ((x) >= (y) ? (x) : (y))
+
+void *
+io_async_init() {
+    fprintf(stderr, "[io_async] not implemented for windows\n");
+    return NULL;
+}
+
+void
+io_async_close(void *arg) {
+    (void)arg;
+}
+
+ssize_t
+io_async_read(int fd, void *buf, size_t count, void *arg) {
+    (void)fd;
+    (void)buf;
+    (void)count;
+    (void)arg;
+    return -1;
+}
+
+ssize_t
+io_async_write(int fd, const void *buf, size_t count, void *arg) {
+    (void)fd;
+    (void)buf;
+    (void)count;
+    (void)arg;
+    return -1;
+}

windows/pci.c

@@ -17,6 +17,11 @@ char pci_path[UMKA_PATH_MAX] = ".";
 __attribute__((stdcall)) uint32_t pci_read(uint32_t bus, uint32_t dev,
                                            uint32_t fun, uint32_t offset,
                                            size_t len) {
+    (void)bus;
+    (void)dev;
+    (void)fun;
+    (void)offset;
+    (void)len;
     printf("STUB: %s:%d", __FILE__, __LINE__);
     return 0xffffffff;
 }

windows/thread.c

@@ -13,6 +13,7 @@ void reset_procmask(void) {
 }
 
 int get_fake_if(void *ctx) {
+    (void)ctx;
     printf("STUB: %s:%d", __FILE__, __LINE__);
     return 0;
 }

windows/vnet/tap.c

@@ -0,0 +1,16 @@
+/*
+    SPDX-License-Identifier: GPL-2.0-or-later
+
+    UMKa - User-Mode KolibriOS developer tools
+    vnet - virtual network card, tap interface
+
+    Copyright (C) 2023  Ivan Baravy <dunkaist@gmail.com>
+*/
+
+#include <stdio.h>
+
+struct vnet *
+vnet_init_tap() {
+    fprintf(stderr, "[vnet] tap interface isn't implemented for windows\n");
+    return NULL;
+}