exif 0.6.22 release

This is the exif release 0.6.22 , a stability and bugfix release.

• New translations: ast, fur, ko, ms, pt_BR, ru, tr
• Updated translations: many!
• Fix a number of compiler and automake warnings
• Fix the --remove option when no tag is specified.
• Escape special XML characters in xml mode.
• Add many continuous integration builds
• Add more regression tests
• Fixup IFD 1 tags when adding or removing a thumbnail.
• Fix the XML tags used in --ids format.
• Fix a memory leak when no arguments are given.
• Enable AM_SILENT_RULES by default.
• Make sure the tag buffer in show_entry_xml is NUL-terminated.
• Eliminated unnecessary remove() calls in jpeg_data_save_file.
• Close files before logging the error.
• Install a SIGPIPE handler to stop generating a signal on pipe failures.
• Fix cross-compilation with pkg-config
• Use GP_CHECK_LIBRARY to look for popt.
• Include strings to translate from libjpeg/jpeg-data.c
• Fixed a double free by initializing data variable to NULL
• Check that JPEGs start with 0xff