Update gtksourceview3 to 3.16.1

News in 3.16.1
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* Update CMake language spec
* Add a "path" class for contexts with a file name
* Performance improvements for groups of text insertions/deletions
* Fix bug with symbolic icons and dark GTK+ theme
* Translation updates

News in 3.16.0
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* A few bug fixes and various other improvements
* Translation updates

News in 3.15.91
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* Fix a crash when destroying the widget during a search
* Add some signals to bind keyboard actions
* Various other improvements
* Translation updates

News in 3.15.90
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* Provide a way to draw background patterns (a grid)
* Support incrementing and decrementing numbers
* Various other improvements

News in 3.15.3
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* Better word boundaries for word selection (double-click) and word movements
  (ctrl+arrow, shift+ctrl+arrow, ctrl+backspace, etc).
* Add style scheme chooser widgets: GtkSourceStyleSchemeChooser (interface),
  GtkSourceStyleSchemeChooserButton and GtkSourceStyleSchemeChooserWidget.
* Add gtk_source_view_indent_lines() and gtk_source_view_unindent_lines().
* Add the GtkSourceView::move-to-matching-bracket action signal.
* Add gtk_source_buffer_join_lines().
* Gutter: use current line background color for current line.
* Add syntax highlighting support for Apache Thrift.
* Various other improvements and bug fixes
* Translation updates

News in 3.15.2
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* Undo/Redo: restore selection
* Documentation improvements
* Some GtkSourceGutter code refactoring
* Syntax highlighting for Apache Pig 0.12

News in 3.15.1
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* Search: allow caller to choose a style for text matches
* gtk_source_completion_context_get_iter() now returns a gboolean to tell if
  the GtkTextIter is correctly set. For a more robust code, it is recommended
  to use the return value.
* Improvements to the Lua and Yacc syntax highlighting
* Translation updates

(prlw1)