initial support for Mega65 extra ROM

c64/kernal/jumptable/fff0.jplot.s

@@ -1,6 +1,11 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
+
 // $FFF0 - Get/Set cursor location vector
 // (http://codebase64.org/doku.php?id=base:kernalreference)
 // To set: C=0, to get, C=1
 // X=row, Y=column
 
 	jmp PLOT
+
+
+#endif // ROM layout