Send stderr of pdfseparate to /dev/null
Send stderr of pdfseparate to /dev/null

There are a few tools, pdfseparate, gs, etc. of which stderror is
displayed. In particular pdfseparate generates the following warning:

    Syntax Warning: PDFDoc::markDictionnary: Found recursive dicts

This stems from the poppler source code. In the `PDFDoc::writeDictionnary`
function in `poppler/PDFDoc.cc`.

dsanson/termpdf