Add KIM-1 functions to write to the 7-segment LED display and get

keypresses from the keypad.
Includes sample program illustrating how to use them.
Tested on real KIM-1 hardware.

libsrc/kim1/getkey.s

@@ -0,0 +1,18 @@
+;
+; int __fastcall__ getkey();
+;
+
+.include        "kim1.inc"
+
+.import         popa
+
+.export         _getkey
+
+.proc           _getkey
+
+        jsr     KEYIN           ; Open up keyboard channel
+        jsr     GETKEY          ; Get key code
+        ldx     #0              ; MSB of return value is zero
+        rts
+
+.endproc

libsrc/kim1/scandisplay.s

@@ -0,0 +1,21 @@
+;
+; void __fastcall__ scandisplay(unsigned char left, unsigned char middle, unsigned char right);
+;
+
+.include        "kim1.inc"
+
+.import         popa
+
+.export         _scandisplay
+
+.proc           _scandisplay
+
+        sta     $F9             ; Rightmost display data
+        jsr     popa
+        sta     $FA             ; Middle display data
+        jsr     popa
+        sta     $FB             ; Leftmost display data
+        jsr     SCANDS
+        rts
+
+.endproc