Added an idle function for long running functions to call.

include/system.h

@@ -10,6 +10,7 @@ extern int strlen(const char *str);
 extern unsigned char inportb (unsigned short _port);
 extern void outportb (unsigned short _port, unsigned char _data);
 extern bool strcmp(char* str1, char* str2);
+extern void idle();
 /* ISRS.C */
 void isrs_install();
 /* This defines what the stack looks like after an ISR was running */