News in 0.2.3
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* GspellLanguage: code improvements, write API documentation and add
  get_default() function
* Add gspell_text_buffer_set/get_spell_checker() functions
* GspellNavigatorGtv renamed to GspellNavigatorText
* Remove GspellNavigatorText:spell-checker property
* GspellInlineCheckerGtv replaced by the higher-level class
  GspellInlineCheckerText
* Language choosers: accept NULL language to pick the default language
* Add the GspellLanguageChooser:language-code property, for a GSettings key
  binding
* GspellChecker: accept a NULL language in case no dictionaries are available
* Other code and documentation improvements
* Translation updates