Added support for setting up a serial port. This first serial driver appears to only work correctly in QEMU.

kernel/io.s

@@ -9,3 +9,13 @@ outb:
 	mov dx, [esp + 4] ; Move the address of the I/O port into the DX register
 	out dx, al		  ; Send the data to the I/O port
 	ret				  ; Return
+	
+global inb
+
+; inb - Returns a byte from the give I/O port.
+; stack: [esp + 4] The address of the I/O port
+;		 [esp    ] The return address
+inb:
+	mov dx, [esp + 4] 	; Move the address of the I/O port to the dx register.
+	in al, dx 			; Read a byte from the I/O port and store it in the al register
+	ret