more work on string support

src/basic/engine/varstr_garbage_collect.s

@@ -4,7 +4,6 @@
 
 // XXX test this routine
 
-// XXX change DSCPNT to use standard descriptor format
 
 varstr_garbage_collect:
 
@@ -323,13 +322,13 @@ varstr_garbage_collect_unused:
 
 	// XXX move these routines to separate files
 
-varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DSCPNT+2
+varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DSCPNT+0
 
-	sta DSCPNT+2 
+	sta DSCPNT+0
 
 	sec
 	lda TXTPTR+0
-	sbc DSCPNT+2 
+	sbc DSCPNT+0 
 	sta TXTPTR+0
 	bcs !+
 	dec TXTPTR+1
@@ -337,13 +336,13 @@ varstr_TXTPTR_down_A:                  // .A - bytes to decrease TXTPTR, uses DS
 	rts
 
 
-varstr_INDEX_up_A:                     // .A - bytes to increase TXTPTR, uses DSCPNT+2
+varstr_INDEX_up_A:                     // .A - bytes to increase TXTPTR, uses DSCPNT+0
 
-	sta DSCPNT+2 
+	sta DSCPNT+0 
 
 	clc
 	lda INDEX+0
-	adc DSCPNT+2 
+	adc DSCPNT+0 
 	sta INDEX+0
 	bcc !+
 	dec INDEX+1