Release notes for 2.18
======================

* gtk_tooltip_set_custom now accept a NULL custom_widget to unset the
  old custom_widget. Custom_widget does not get destroyed when the
  tooltip goes away.

* JPEG2000 support is no longer enabled by default. It must be
  explicitly turned on, by passing --with-libjasper to configure.

* GDK has been reworked to implement 'client-side windows'. This offers
  exciting new possibilities, such as transformed, offscreen rendering,
  but it breaks some long-standing assumptions that applications may
  have about GDK windows. Setting the environment variable
  GDK_NATIVE_WINDOWS makes GDK create a native X11 window for each
  GDK window, which might make problematic applications work better.