Since meson 0.43.0 (below our current requirement), 'symbol_prefix'
argument of gnome.generate_gir() allows an ordered list. If I prepend
'gimp_ui', it makes any gimp_ui_*() function to not start with 'ui_'.
In particular, GimpUi.ui_init() becomes GimpUi.init() which is much less
redundant.
Since the patch was initially contributed, some parts of the
introspection changed. First all GUI-related code is in a GimpUi module
now.
Also Gimp.get_pdb().run_procedure() is now using a list instead of a
GimpValueArray.
