gdk-pixbuf 2.42.4 release:

• Make enum type registration thread safe
• Do not install skipped test files [Jan Tojnar]
• Fix GIF initialization [Simon McVittie]
• Always run GIF loader tests [Simon McVittie]
• Fix leaks discovered via ASan [Simon McVittie]
• Expose GdkPixbufLoader API via introspection [Paolo Borelli]
• Fix revert-to-previous first frame behaviour for GIF files [Robert Ancell, #166]
• Link to libintl if needed [Fabrice Fontaine]
• Improve support for using gdk-pixbuf as a subproject [Xavier Claessens]
• Fix build with GModule disabled [Fabrice Fontaine]
• Use gi-docgen to generate the API reference from introspection data

This build also disables gtk-doc documentation as we don't have gi-docgen in Fedora yet.