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/network/pcap_if.c

@@ -54,9 +54,9 @@
 #include <ctype.h>
 #include <pcap/pcap.h>
 #include <time.h>
-#include "86box.h"
-#include "plat.h"
-#include "plat_dynld.h"
+#include <86box/86box.h>
+#include <86box/plat.h>
+#include <86box/plat_dynld.h>
 
 
 static void	*pcap_handle;		/* handle to WinPcap DLL */