add almost full vfd implementation

board/vfd-frame.h

@@ -0,0 +1,20 @@
+#pragma once
+
+#include <windows.h>
+
+#include <stddef.h>
+#include <stdint.h>
+
+#include "hook/iobuf.h"
+
+enum {
+    VFD_SYNC_BYTE = 0x1B,
+    VFD_SYNC_BYTE2 = 0x1A,
+};
+
+bool vfd_frame_sync(struct const_iobuf *src);
+
+HRESULT vfd_frame_encode(
+        struct iobuf *dest,
+        const void *ptr,
+        size_t nbytes);