Benchmark: EnwikiDocMaker does not use fileIn (BufferedReader)

[Shai Erera]

I started working on the patch for 1591, and noticed EnwikiDocMaker uses the
FileInputStream instance from LineDocMaker and not the BuferredReader. I
don't see any reason to this, as InputSource accepts a Reader. I can change
it as part of 1591, unless you think I'm missing something.