libcupsfilters: In pwgtoraster() with PPD do not modify header via IPP options

libcupsfilters: In pwgtoraster() with PPD do not modify header via IPP options

In the pwgtoraster() filter function, if we have a PPD file, we do not
call cupsRasterParseIPPOptions() as it sets the Raster header entries
solely by the names and choice names of the IPP attributes and command
line options, regardless of what the PPD supports. This broke some
jobs.

If we have a PPD, we need to convert IPP attributes into proper PPD
options before calling the filter functions (what is done by
libpappl-retrofit for example).