Implemented the National Semiconductors PC87307, PC87309, PC87332, and PC97307 Super I/O chips, fixed a number of bugs, and removed two machines from the Dev branch due to them now having the correct Super I/O chips.

src/device/serial.c

@@ -597,6 +597,9 @@ serial_read(uint16_t addr, void *p)
 void
 serial_remove(serial_t *dev)
 {
+    if (dev == NULL)
+	return;
+
     if (!serial_enabled[dev->inst])
 	return;
 
@@ -616,6 +619,9 @@ serial_setup(serial_t *dev, uint16_t addr, int irq)
 {
     serial_log("Adding serial port %i at %04X...\n", dev->inst, addr);
 
+    if (dev == NULL)
+	return;
+
     if (!serial_enabled[dev->inst])
 	return;
     if (dev->base_address != 0x0000)