Log Message:
vala: update to 0.56.6

Vala 0.56.6
===========
 * Regression fix:
  - vala: Improve initialization of namespace fields with compound
    literal

 * Bindings:
  - gio-2.0,glib-2.0,gobject-2.0: Update 2.74 symbols
  - webkit2gtk-4.*: Update to 2.40.0
  - webkitgtk-6.0: Update to 2.40.0