Bump to version 0.21
    
      * zbarcam-qt: allow selecting codes via GUI interface
      * When both enabled, ISBN-13 has precedence over ISBN-10
      * ZBar is now using Travis CI for continuous integration tests
      * Convert INSTALL and README to markdown and update them
      * Improve ZBar testing code and make easier to run the tests
      * Fix build with Clang
      * Add simple dbus IPC API to zbarcam.
      * zbarimg: display only the compiled symbologies
      * v4l2: make ZBar build and run on Kernels < 3.16
      * configure.ac: The pdf417 code is incomplete. Warn about that
      * Add Debian packaging and Travis CI configuration
      * Add barcode examples for different supported symbologies
      * Several improvements at the building system
      * Add support for SQ code symbology
      * v4l2: add fallback for systems without v4l2_ext_controls which field
      * v4l2: use device_caps instead of capabilities
      * v4l2: make v4l2_request_buffers() more generic
      * release video buffers after probing and request them again when needed
      * Ignore ENOTTY errors when calling VIDIOC_S_CROP
      * doc/Makefile.am.inc: clean html generated files
      * Add --disable-doc configure option to disable building docs
      * Fix function protoype to be compatible with recent libjpeg
      * Wrap logical not operations into parentheses
      * INSTALL: warn that autoconf should be called before configure
      * code128: fix error logic
      * convert: ensure that it will not use a freed value
      * zbar: use g_thread_new() instead of g_tread_create()
      * zbargtk: add a missing break
      * gtk/zbargtk: add a missing check if zbar->window is not null
    
    Signed-off-by: Mauro Carvalho Chehab <mchehab+samsung@kernel.org>