Ported the cassette emulation from PCE, closes #835.

src/machine/machine.c

@@ -27,6 +27,7 @@
 #include <86box/86box.h>
 #include <86box/device.h>
 #include <86box/timer.h>
+#include <86box/cassette.h>
 #include <86box/dma.h>
 #include <86box/pic.h>
 #include <86box/pit.h>
@@ -90,6 +91,9 @@ machine_init_ex(int m)
 	smbase = is_am486dxl ? 0x00060000 : 0x00030000;
 
 	lpt_init();
+
+	if (cassette_enable)
+		device_add(&cassette_device);
     }
 
     /* All good, boot the machine! */