cups-filters: Update print/cups-filters to 1.20.1

Changes:
1.20.1
------
- libcupsfilters: Silenced warning when using CUPS < 2.x by
  eliminating the use of a recently introduced CUPS library
  function (Bugzilla bug #1421).
- braille: Fix some missing options on indexv4. Thanks to
  Samuel Thibault for this patch (Pull request #21).
- braille: Fix disabling margins on indexv4 in graphic
  mode. Thanks to Samuel Thibault for this patch (Pull request
  #20).
- braille: Fix installation of brftopagedbrf. Thanks to Samuel
  Thibault for this patch (Pull request #18, Issue #17).
- cups-browsed: Fixed crash when CUPS reports a print queue
  without "device-uri" attribute when cups-browsed polls a
  list of local CUPS queues (Issue #16).

1.20.0
------
- libcupsfilters: Let the PPD generator prefer the English
  translation file from CUPS for the human-readable strings in
  the PPD files.
- libcupsfilters: The PPD generator lists all page sizes with
  human-readable names now, including proprietary names of the
  printer.
- cups-browsed, driverless: Fixed get-printer-attributes call
  on driverless printers for generating the PPD, explicitly
  requesting the media-col-database attribute as otherwise
  borderless page sizes do not appear.
- libcupsfilters: Fixed loading option/choice strings lists
  from driverless printers for PPD file generation. Especially
  proprietary media types appear correctly now.
- libcupsfilters: Completed color space support in the PPD
  generator: Added DeviceGray/RGB/CMYK, default to 8 bit for
  SRGB and to 16 bit for AdobeRGB, avoid duplicate listings of
  the same color space.

1.19.0
------
- libcupsfilters: Let the PPD generator add the options "Print
  Optimization", "Print Rendering Intent" and "Print Scaling"
  if appropriate IPP attributes are found.
- libcupsfilters: Let the PPD generator read out the maximum
  of info about color spaces and this way not only reliably
  the correct choices are added to the ColorModel option but
  also the maximum supported bit depth (8 or 16 bit) is used.
- libcupsfilters: Overtaken new features from CUPS' PPD
  generator: Presets, Finishing Templates, and extraction of
  media sizes from "media-col-database"
- libcupsfilters: Improvements on header of generated PPDs:
  use cups-filters version number, "drvless.ppd" PCFileName,
  APSupplies and cupsChargeInfoURI from CUPS.
- libcupsfilters: Let the PPD generator use the IPP string
  tables in the translation files of CUPS 2.3.x or newer
  (English strings only). Let all options in the PPD have
  human-readable option and choice names. In case of CUPS
  2.2.x or older (or if the CUPS translation are missing) we
  fall back to internal tables.
- cups-browsed: Improved debug output when checking IPP
  attributes of IPP printers.
- .gitignore: Ignore also core files.
- cups-browsed: Support use of PPD files generated by CUPS for
  IPP Printers. Works only if the the local queue created by
  cups-browsed replaces a temporary queue from CUPS.
  Configurable via "UseCUPSGeneratedPPDs" directive in
  cups-browsed.conf.

1.18.0
------
- braille: Add support for page-ranges option. Thanks to
          Samuel Thibault for this patch (Pull request #12).
- braille: Fix supporting docx and LO file names with
          spaces. Thanks to Samuel Thibault for this patch (Pull
          request #11).
- .gitignore: Updated and cleaned up.
- Build system: Make sure that "make dist" always includes all
  files of the repository, plus the files generated by
  ./autogen.sh, independent of the system configuration and
  the used ./configure options.
- pdftoijs, pdftoopvp: Build pdftoijs and pdftoopvp only on
  demand (via "--enable-ijs" and "--enable-opvp" on the
  ./configure command line). There are actually no known
  printer drivers using these filters. If no one complains
  about the missing filters they will get completely removed.
- Build system: Set default path for pdftops to
  /usr/bin/pdftops also for cross-compiling (Bug #1417).
- cups-browsed: Set "printer-location" as an attribute and not
  as an option when creating/updating a CUPS queue (Bug
  #1413).
- braille: Fix handling non-printable characters in BRF
  files. Thanks to Samuel Thibault for this patch.
- braille: Fix printing backslashes in BRF files. Thanks to
  Samuel Thibault for this patch.
- braille: use application/vnd.cups-brf instead of
  text/vnd.cups-brf. Thanks to Samuel Thibault for this patch.
- braille: Make sure liblouis emits pure BRF output. Thanks to
  Samuel Thibault for this patch.
- braille: Spaces at the head of lines were not getting
  embossed, because bash would eat them in the read
  command. IFS allows to avoid the issue. Thanks to Samuel
  Thibault for this patch.
- gstoraster: Emit proper error message if Ghostscript is
  missing.  Thanks to Peter De Wachter (pdewacht at gmail dot
  com) for the patch (Bug #1415).
- braille: Old bash does not like quotes, like in '$(("123" +
  0))'. Removed unneeded quotes. Thanks to Samuel Thibault for
  this patch.
- braille: Index V5 embossers are compatible with the V4
  protocol so we do not need driver changes, we just need to
  advertise the support. Thanks to Samuel Thibault for this
  patch.

(leot)