GTK+ Gets a Major Bugfix Update Ahead of GNOME 3.16

GTK+ 3.15.11 fixes an issue with the FileFilter name not being set, allows compiling with the –disable-xkb argument by addressing the undefined references to the get_xkb(), makes sincos portable, makes the titlebar of Gedit draggable again, and makes sure that text can be highlighted in GtkInfoBar.