Windows make test portability

More progress on the Windows portability: 
 * IO::Socket should be avoided, causes some weird problems. So made the call in latexmlc even more defensive
 * $kpsewhich  may have unescaped spaces under Windows, so I now explicitly quoted the invocation to ```"$kpsewhich```.
 * addNodes in LaTeXML::Post::Document was iterating through the keys of a hash without a "sort" and adding attributes. So added a "sort" to make the output reproducible in Perl 5.18+

I tested in both Windows and Linux, and the patches seem to be acting as expected. This is ready to be merged.

The only remaining failures I am seeing in the Windows ```make test``` come from not having Image::Magick installed, so I will try to install it now (that's a huge pain under Windows 8).