Remove trailing whitespace

[LiuYinCarl]

There are some trailing whitepace in the fanyi buffer, I think may be we can remove them, It will be better for the users who are using white-space-mode.

use the following setting to see trailing whitespace

(setq-default show-trailing-whitespace t)

[condy0919]

我居然才看到，这个东西可以有！