implemented SCREEN routine

c64/kernal/ffed.s

@@ -1,4 +1,4 @@
 ; $FFED - Return screen size (X=columns, Y=rows)
 ; (http://codebase64.org/doku.php?id=base:kernalreference)
 
-	jmp get_screen_size
+	jmp screen

c64/kernal/get_screen_size.s

@@ -1,2 +0,0 @@
-get_screen_size:
-	rts

c64/kernal/screen.s

@@ -0,0 +1,11 @@
+; Function defined on p295 of C64 Programmers Reference Guide
+
+screen:
+
+	;; There are only 2 sane ways to implement this routine,
+	;; I hope this one is different than what Commodore picked :)
+
+	ldy #25 ; 25 columns
+	ldx #40 ; 40 rows
+
+	rts