Added very basic interactive shell.

include/shell.h

@@ -0,0 +1,8 @@
+#ifndef __SHELL_H
+#define __SHELL_H
+
+void run_shell();
+void key_pressed(unsigned char* character);
+void execmd();
+
+#endif

include/system.h

@@ -9,6 +9,7 @@ extern unsigned short *memsetw(unsigned short *dest, unsigned short val, int cou
 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);
 /* ISRS.C */
 void isrs_install();
 /* This defines what the stack looks like after an ISR was running */