Kernel: Make both Ioctl.h and POSIX/termios.h define struct winsize

FreeBSD also makes it available from both sys/ioctl.h and termios.h.
glibc doesn't have the POSIX 2024 tc{set,get}winsize() wrappers yet,
so it doesn't even define it in termios.h at the moment.

LLVM relies on sys/ioctl.h defining struct winsize, so the llvm port and
the zig port failed to build after 312b4440bf.

Kernel/API/Ioctl.h

@@ -7,6 +7,8 @@
 
 #pragma once
 
+#include <Kernel/API/POSIX/winsize.h>
+
 #ifdef __cplusplus
 extern "C" {
 #endif

Kernel/API/POSIX/termios.h

@@ -7,6 +7,7 @@
 #pragma once
 
 #include <Kernel/API/POSIX/sys/types.h>
+#include <Kernel/API/POSIX/winsize.h>
 
 #ifdef __cplusplus
 extern "C" {
@@ -28,14 +29,6 @@ struct termios {
     speed_t c_ospeed;
 };
 
-// https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/termios.h.html#tag_14_77_03_07
-struct winsize {
-    unsigned short ws_row;
-    unsigned short ws_col;
-    unsigned short ws_xpixel;
-    unsigned short ws_ypixel;
-};
-
 /* c_cc characters */
 #define VINTR 0
 #define VQUIT 1

Kernel/API/POSIX/winsize.h

@@ -0,0 +1,23 @@
+/*
+ * Copyright (c) 2026, Sönke Holz <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#pragma once
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/* https://pubs.opengroup.org/onlinepubs/9799919799/basedefs/termios.h.html#tag_14_77_03_07 */
+struct winsize {
+    unsigned short ws_row;
+    unsigned short ws_col;
+    unsigned short ws_xpixel;
+    unsigned short ws_ypixel;
+};
+
+#ifdef __cplusplus
+}
+#endif