libppd 2.0rc2

Bug fixes following first bug reports from Ubuntu 23.04 and Fedora 38 users, first distros with libcupsfilters 2.0rc1, and also synced the code with current CUPS, 3 years after it was spun out, adding a lot more bug fixes and some extra PPD attributes in auto-generated PPDs to make full use of CUPS' functionality:

• ppdFilterPSToPS(): Fixed reverse output order.
  When converting the former pstops CUPS filter into the filter function, some function calls got wrongly replaced by new ones, resulting in no output at all when the input should be re-arranged into reverse order. This broke printing with all PostScript printers (and proprietary CUPS drivers needing PostScript as input) which do reverse-order by default (Issue #20, Ubuntu bug #2022943).
• Fixed resolution handling when converting PPDs to printer IPP attributes
  For PWG/Apple Raster or PCLm output resolutions in job options or pseudo-PostScript code in the PPD get ignored and instead, the lowest resolution of the description of the Raster format used in the PPD file gets always used, which reduced output quality (Ubuntu bug #2022929).
• ppdFilterLoadPPD(): Actually create sample Raster header also for Apple/PWG Raster
• All PPD files with "MirrorPrint" option cuased mirrored printout
  If a PPD contains an option "MirrorPrint", the ppdFilterLoadPPD() sent the option mirror=true to the filter functions, regardless of the actual setting of "MirrorPrint" (which is usually "False" by default), making all jobs coming out with mirrored pages (Ubuntu bug #2018538).
• PPD file generator: Put *cupsSingleFile: True into generated PPD as some driverless IPP printers do not support multi-file jobs (CUPS issue #643).
• Add CUPS PPD attributes *cupsLanguages: ... and *cupsStringsURI ... to generated PPDs so that CUPS loads printer-specific option names and translations from the printer and uses them without need of static translations in the PPD file.
• CUPS renames the PPD option choice name "Custom" to "_Custom" when a fixed choice is named as such, to distinguish from CUPS' facility for custom option values. We do now the same when loading PPD files.
• Prevent duplicate PPD->IPP media-type name mappings, now we do not have dropping of some media types in the Printer Applications any more.
• When not specifying a media source and the page size is small (5x7" or smaller) do not request the photo tray but auto instead.
• Do not override color settings from print dialog ("ColorModel") with print-color-mode setting.
• Make ppdFilterPSToPS() recognize %%PageRequirements: DSC comment.
• Correctly display "Xprinter" instead of Xerox for Xprinter devices
• Fix the job-pages-per-set value (used to apply finishings correctly) for duplex and N-up printing.
• Make the testppd build test program also work if it is started from an environment with non-English locale.
• Minor bug fixes, silencing warnings (especially of clang), fixing typos in comments, coding style, ..., and also some fixes for memory leaks.