Fix for pdfinfo changes in poppler-utils 0.48
PDF metadata querying was done with pdfinfo's "-meta" and "-l" options
at the same time, which was supported in poppler 0.26 but not in
Upstream change: https://bugs.freedesktop.org/show_bug.cgi?id=96801
Local change is to run the two as separate commands, then send the
output together into the existing processing. Should work with older
poppler-utils on Jessie as well as current one on Stretch.