reordered and size-optimized some screen routines

c64/kernal/screen/screen_code_to_petscii.s

@@ -0,0 +1,36 @@
+
+screen_code_to_petscii:
+	cmp #$1B
+	bcc s2p_adc_40
+	
+s2p_not_alpha:
+	cmp #$40
+	bcc s2p_end
+
+	// FALLTROUGH
+
+s2p_not_punctuation:
+	cmp #$5B
+	bcs s2p_not_shifted
+
+	// carry already clear here
+	adc #$80
+
+	rts
+
+s2p_not_shifted:
+
+	cmp #$80
+	bcs s2p_end // not vendor
+
+	// $60-$7F -> $A0-$BF
+
+s2p_adc_40:
+
+	clc
+	adc #$40
+	
+	// FALLTROUGH
+
+s2p_end:
+	rts