Added an I/O port driver and made it callable from C.

includes/io.h

@@ -0,0 +1,4 @@
+#ifndef IO_H
+#define IO_H
+void outb(unsigned short port, unsigned char data);
+#endif

kernel/io.s

@@ -0,0 +1,11 @@
+global outb
+
+; outb - Send a byte to an I/O port.
+; stack: [esp + 8] The data byte
+; 		 [esp + 4] The I/O port
+;		 [esp	 ] Return address
+outb:
+	mov al, [esp + 8] ; Move the data to send into the AL register
+	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