Bug 1020847 - Add handwriting IME for Simplified Chinese.

I will give a comment for `_strokePoints`, describing its data format. 
It's a 1d array,  in the c code of handwriting recognition engine,  it's much more complex to manage memory for 2d array, and its length is variable.
Now, most c recognition engine is implemented with 1d arry format, so we just keep consistent with it.

There are two internal IME API,  setLang and recognize, I will write some comments for them. Thanks you.