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/hwm.c

@@ -15,8 +15,8 @@
  */
 
 #include <stdint.h>
-#include "device.h"
-#include "hwm.h"
+#include <86box/device.h>
+#include <86box/hwm.h>
 
 
 hwm_values_t hwm_values;