Move all include files to src/include

- 86Box's own headers go to /86box
- munt's public interface goes to /mt32emu
- all slirp headers go to /slirp (might want to consider using only its public inteface)
- single file headers from other projects go in include root

src/video/vid_ht216.c

@@ -21,17 +21,17 @@
 #include <string.h>
 #include <stdlib.h>
 #include <wchar.h>
-#include "86box.h"
+#include <86box/86box.h>
 #include "cpu.h"
-#include "86box_io.h"
-#include "mem.h"
-#include "timer.h"
-#include "pic.h"
-#include "rom.h"
-#include "device.h"
-#include "video.h"
-#include "vid_svga.h"
-#include "vid_svga_render.h"
+#include <86box/io.h>
+#include <86box/mem.h>
+#include <86box/timer.h>
+#include <86box/pic.h>
+#include <86box/rom.h>
+#include <86box/device.h>
+#include <86box/video.h>
+#include <86box/vid_svga.h>
+#include <86box/vid_svga_render.h>
 
 
 typedef struct ht216_t