Fixes a rendering problem of certain CJK fonts

I recently switched to a new Chinese font on my computer and noticed
that it is not rendered correctly. The glyphs seemed to have been shifted downward.

Before this patch was applied:
![before](https://f.cloud.github.com/assets/3608694/231924/21e7e4be-871a-11e2-9f86-5b32b83b923e.png)
If you look closely enough you will find that the Chinese line appeared to be
shifted down some pixels.

After this patch was applied:
![after](https://f.cloud.github.com/assets/3608694/231926/425229d0-871a-11e2-9915-eb5277ba01ec.png)
Now the Chinese characters are rendered correctly.

I tested other fonts (CJK and Latin) I have on my computer and this patch solved the
rendering problem while not causing regressions (Latin glyphs continue to appear normal).