In XORShiftRandom.scala, use val "million" instead of constant "1e6.toInt".
Delete vals that never used in other files.

Author: WangTao <barneystinson@aliyun.com>

Closes #565 from WangTaoTheTonic/master and squashes the following commits:

17cacfc [WangTao] Handle the unused assignment, method parameters and symbol inspected by Intellij IDEA
37b4090 [WangTao] Handle the vals that never used