Make screensize() fetch the values dynamically instead of using variables

that are set on startup. This is needed to support the C128, which can switch
the screen size at runtime.


git-svn-id: svn://svn.cc65.org/cc65/trunk@2042 b7a2c559-68d2-44c3-8de9-860c34a00d81

libsrc/pet/clrscr.s

@@ -7,7 +7,6 @@
 	.export	    	_clrscr
 	.import		plot
        	.importzp   	ptr1
-	.import	    	xsize
 
 	.include    	"pet.inc"
 
@@ -23,9 +22,9 @@ _clrscr:
 ; Determine, how many pages to fill
 
 	ldx 	#4
-	lda	xsize
-	cmp	#40
-       	beq	L1
+	lda	SCR_LINELEN     ; Check length of one line
+	cmp	#40+1
+       	bcc    	L1
 	ldx	#8
 
 ; Clear the screen