basic: parsing FOR statement, FOR itself still broken :(

assets/tbas/syntax.txt

@@ -7,7 +7,7 @@ linenumber = digits ;
 
 stmt =
       "IF" , expr_sans_asgn , "THEN" , stmt , ["ELSE" , stmt]
-    | "FOR" , expr  // TODO
+    | "FOR" , expr
     | "DEFUN" , [ident] , "(" , [ident , {" , " , ident}] , ")" , "=" , expr
     | "ON" , expr_sans_asgn , ("GOTO" | "GOSUB") , expr_sans_asgn , {"," , expr_sans_asgn}
     | "(" , stmt , ")"