Load image from byte arary

Leptonica does not support reading images from memory on Windows, but it is nice to provide an alternate approach where you write the contents of the byte array to a temporary file. The temporary file is removed during dispose. 

Test cases are included.

A issue regarding the matter has been filed here:
https://code.google.com/p/leptonica/issues/detail?id=77

I doubt fmemopen will make it's way into leptonica, so this will probably end up being a long-term solution.