libcupsfilters: Added PWG/Apple Raster support to pwgtoraster()

libcupsfilters: Added PWG/Apple Raster support to pwgtoraster()

The pwgtoraster() filter function is now able to also output PWG
Raster and Apple Raster, for direct conversion between PWG and Apple
Raster without inbetween CUPS Raster step. Also CUPS Raster based on
PCLm info in the PPD or in the printer IPP attributes for feeding into
rastertopclm is supported.

With this we can for example use MuPDF via the mupdftoraster() filter
function which has only PWG Raster output for all driverless printing
formats (Apple Raster, PWG Raster, PCLm) and also for classic CUPS
Raster drivers (CUPS Raster format).

Selection of the ourput format is done via the parameters, like with
the other filter functions.

We also allow the overspray/rounding correction kick in on jobs where
the output page size is not explicitly requested, as rounding errors
can always happen. Page size dimensions in the PPD can easily deviate
from the exact dimensions of the input pages.