Created by: ZHUI

In the /paddle/fluid/operators/math/sequence2batch.h#L122.

The type of max_seqlen is int. If we carefully set max_seqlen= 2147483647, then max_seqlen + 1 will be -2147483648 . Thus may cause integer overflow problem.

Please reference more deatails in http://newicafe.baidu.com/issue/77812981/show?cid=5&spaceId=23205