cups-browsed 2.0rc1

Release Candidate: Prefer Apple Raster against PDF, and fix implicitclass backend crash.

• Prefer sending jobs in Apple Raster instead of in PDF
  If a destination printer supports both PDF and Apple Raster, and if it is not a remote CUPS queue, prefer sending the job in Apple Raster, as printers print this more reliably (Ubuntu bug 2014976)
• run-tests.sh: Let emulated printers support PDF input
  To test that cups-browsed prefers Apple Raster when the printer supports both PDF and Apple Raster as input format, we let the printers emulated by ippeveprinter also support PDF.
• implicitclass backend: NULL-initialize filter data field for Raster header
  We are running a filter chain without PPD file, so we do not have Raster header, so initialize it to NULL.