cups-filters 1.28.17

Bug fix release, to more reliably discover all printer capablities from driverless printers, especially borderless printing, and to preferably use Apple Raster instead of PWG Raster or PCLM.

• libcupsfilters: In PPD generator create only one *cupsFilter2: line for raster. Only use the most desirable/reliable format, usually Apple Raster (Issue #498).
• libcupsfilters: In get_printer_attributes() poll media-col-database separately if needed. On some printers one gets media-col-database only this way. Often it reveals important functionality, like for example borderless printing (Issue #492).
• libcupsfilters: Let PPD generator also parse media-col-ready IPP attribute. media-col-ready lists the loaded media, in contrary to media-ready, as list of complete descriptions of the media (media-col data structure). This often lists also variants like borderless (it is the same physical paper). Especially useful when media-col-database is not available (Issue #492).
• libcupsfilters: In generate_sizes() consider all margin alternatives. When generating the PPD file for a driverless printer, and in the media-{left,right,top,bottom}-margin-supported printer IPP attributes there was more than 1 value, the first value (which often was the 0 for borderless printing) was not considered, leaving the borderless functionality of many printers undiscovered (Issue #492).