need to fix the prettyprint

1>fix the bug of ast.java about If and While.Now,they can deal with the
multi-stmts.
2>int the Fac.java,add a ast of Sum.java.
3>fix the bug of args display
Revert "need to fix the prettyprint"

This reverts commit c042ef28102e2015c76e4a53bc4c33048447cbac.
Revert "Revert "need to fix the prettyprint""

This reverts commit e2362bf9466e8eb950eab57bb0c22bc30feed162.